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NAME

       tcsh - C shell with file name completion and command line editing

SYNOPSIS

       tcsh [-bcdefFimnqstvVxX] [-Dname[=value]] [arg ...]
       tcsh -l

DESCRIPTION

       tcsh  is  an enhanced but completely compatible version of the Berkeley
       UNIX C shell, csh(1).  It is a command language interpreter usable both
       as an interactive login shell and a shell script command processor.  It
       includes  a  command-line  editor  (see   The   command-line   editor),
       programmable  word  completion  (see  Completion and listing), spelling
       correction (see Spelling correction), a history mechanism (see  History
       substitution),  job  control  (see  Jobs) and a C-like syntax.  The NEW
       FEATURES section describes major  enhancements  of  tcsh  over  csh(1).
       Throughout  this  manual,  features  of  tcsh  not found in most csh(1)
       implementations (specifically, the 4.4BSD csh) are labeled with  ‘(+)’,
       and features which are present in csh(1) but not usually documented are
       labeled with ‘(u)’.

   Argument list processing
       If the first argument (argument 0) to the shell is ‘-’  then  it  is  a
       login shell.  A login shell can be also specified by invoking the shell
       with the -l flag as the only argument.

       The rest of the flag arguments are interpreted as follows:

       -b  Forces a ‘‘break’’ from  option  processing,  causing  any  further
           shell  arguments  to  be  treated  as  non-option  arguments.   The
           remaining arguments will not be interpreted as shell options.  This
           may  be used to pass options to a shell script without confusion or
           possible subterfuge.  The shell will not run a set-user  ID  script
           without this option.

       -c  Commands  are  read  from  the  following  argument  (which must be
           present, and must be a single  argument),  stored  in  the  command
           shell   variable   for  reference,  and  executed.   Any  remaining
           arguments are placed in the argv shell variable.

       -d  The shell loads the directory stack from  ~/.cshdirs  as  described
           under Startup and shutdown, whether or not it is a login shell. (+)

       -Dname[=value]
           Sets the environment variable name to value. (Domain/OS only) (+)

       -e  The shell exits if any invoked  command  terminates  abnormally  or
           yields a non-zero exit status.

       -f  The shell ignores ~/.tcshrc, and thus starts faster.

       -F  The  shell  uses  fork(2)  instead  of vfork(2) to spawn processes.
           (Convex/OS only) (+)

       -i  The shell is interactive and prompts for its top-level input,  even
           if it appears to not be a terminal.  Shells are interactive without
           this option if their inputs and outputs are terminals.

       -l  The shell is a login shell.  Applicable only if -l is the only flag
           specified.

       -m  The  shell  loads  ~/.tcshrc  even  if  it  does  not belong to the
           effective user.  Newer versions of su(1) can pass -m to the  shell.
           (+)

       -n  The  shell parses commands but does not execute them.  This aids in
           debugging shell scripts.

       -q  The shell accepts SIGQUIT (see Signal handling) and behaves when it
           is used under a debugger.  Job control is disabled. (u)

       -s  Command input is taken from the standard input.

       -t  The  shell reads and executes a single line of input.  A ‘\’ may be
           used to escape the newline at the end of  this  line  and  continue
           onto another line.

       -v  Sets  the  verbose  shell variable, so that command input is echoed
           after history substitution.

       -x  Sets  the  echo  shell  variable,  so  that  commands  are   echoed
           immediately before execution.

       -V  Sets the verbose shell variable even before executing ~/.tcshrc.

       -X  Is to -x as -V is to -v.

       --help
           Print a help message on the standard output and exit. (+)

       --version
           Print  the  version/platform/compilation  options  on  the standard
           output and exit.  This information is also contained in the version
           shell variable. (+)

       After processing of flag arguments, if arguments remain but none of the
       -c, -i, -s, or -t options were given, the first argument  is  taken  as
       the  name  of  a  file of commands, or ‘‘script’’, to be executed.  The
       shell opens this file and saves its name for possible resubstitution by
       ‘$0’.   Because  many  systems  use  either  the  standard version 6 or
       version 7 shells whose shell  scripts  are  not  compatible  with  this
       shell, the shell uses such a ‘standard’ shell to execute a script whose
       first character is not a ‘#’, i.e., that does not start with a comment.

       Remaining arguments are placed in the argv shell variable.

   Startup and shutdown
       A  login  shell  begins  by  executing  commands  from the system files
       /etc/csh.cshrc and /etc/csh.login.   It  then  executes  commands  from
       files  in  the  user’s  home  directory:  first  ~/.tcshrc  (+)  or, if
       ~/.tcshrc is not found, ~/.cshrc, then ~/.history (or the value of  the
       histfile shell variable), then ~/.login, and finally ~/.cshdirs (or the
       value of  the  dirsfile  shell  variable)  (+).   The  shell  may  read
       /etc/csh.login  before  instead  of  after /etc/csh.cshrc, and ~/.login
       before instead of after ~/.tcshrc or ~/.cshrc  and  ~/.history,  if  so
       compiled; see the version shell variable. (+)

       Non-login  shells read only /etc/csh.cshrc and ~/.tcshrc or ~/.cshrc on
       startup.

       For     examples     of     startup     files,      please      consult
       http://tcshrc.sourceforge.net.

       Commands  like  stty(1)  and  tset(1),  which need be run only once per
       login, usually go in one’s ~/.login file.  Users who need  to  use  the
       same  set  of  files with both csh(1) and tcsh can have only a ~/.cshrc
       which checks for the existence of the tcsh shell variable (q.v.) before
       using  tcsh-specific  commands,  or  can  have  both  a  ~/.cshrc and a
       ~/.tcshrc which sources (see the builtin command) ~/.cshrc.   The  rest
       of  this manual uses ‘~/.tcshrc’ to mean ‘~/.tcshrc or, if ~/.tcshrc is
       not found, ~/.cshrc’.

       In the  normal  case,  the  shell  begins  reading  commands  from  the
       terminal, prompting with ‘> ’.  (Processing of arguments and the use of
       the shell to process files containing  command  scripts  are  described
       later.)   The shell repeatedly reads a line of command input, breaks it
       into words, places it on  the  command  history  list,  parses  it  and
       executes each command in the line.

       One can log out by typing ‘^D’ on an empty line, ‘logout’ or ‘login’ or
       via  the  shell’s  autologout  mechanism  (see  the  autologout   shell
       variable).   When  a  login  shell  terminates it sets the logout shell
       variable to ‘normal’  or  ‘automatic’  as  appropriate,  then  executes
       commands  from  the files /etc/csh.logout and ~/.logout.  The shell may
       drop DTR on logout if so compiled; see the version shell variable.

       The names of the system login and logout  files  vary  from  system  to
       system for compatibility with different csh(1) variants; see FILES.

   Editing
       We  first describe The command-line editor.  The Completion and listing
       and Spelling correction sections describe  two  sets  of  functionality
       that  are  implemented  as  editor commands but which deserve their own
       treatment.  Finally, Editor commands lists  and  describes  the  editor
       commands specific to the shell and their default bindings.

   The command-line editor (+)
       Command-line  input  can  be edited using key sequences much like those
       used in GNU Emacs or vi(1).  The editor is active only  when  the  edit
       shell  variable  is  set, which it is by default in interactive shells.
       The bindkey builtin can display and change key  bindings.   Emacs-style
       key  bindings  are  used  by  default  (unless  the  shell was compiled
       otherwise; see the version shell variable), but bindkey can change  the
       key bindings to vi-style bindings en masse.

       The  shell  always  binds  the  arrow  keys  (as defined in the TERMCAP
       environment variable) to

           down    down-history
           up      up-history
           left    backward-char
           right   forward-char

       unless doing so would alter another single-character binding.  One  can
       set  the  arrow  key escape sequences to the empty string with settc to
       prevent these bindings.  The ANSI/VT100 sequences for  arrow  keys  are
       always bound.

       Other  key  bindings are, for the most part, what Emacs and vi(1) users
       would expect and can easily be displayed by bindkey,  so  there  is  no
       need to list them here.  Likewise, bindkey can list the editor commands
       with a short description of each.

       Note that editor commands do not have the same notion of a ‘‘word’’  as
       does  the  shell.   The editor delimits words with any non-alphanumeric
       characters not  in  the  shell  variable  wordchars,  while  the  shell
       recognizes  only  whitespace  and  some  of the characters with special
       meanings to it, listed under Lexical structure.

   Completion and listing (+)
       The shell  is  often  able  to  complete  words  when  given  a  unique
       abbreviation.  Type part of a word (for example ‘ls /usr/lost’) and hit
       the tab key  to  run  the  complete-word  editor  command.   The  shell
       completes the filename ‘/usr/lost’ to ‘/usr/lost+found/’, replacing the
       incomplete word with the complete word in the input buffer.  (Note  the
       terminal ‘/’; completion adds a ‘/’ to the end of completed directories
       and a space to the end of other completed words, to  speed  typing  and
       provide  a  visual  indicator  of successful completion.  The addsuffix
       shell variable can be unset to prevent this.)  If  no  match  is  found
       (perhaps ‘/usr/lost+found’ doesn’t exist), the terminal bell rings.  If
       the word is already complete (perhaps there is a  ‘/usr/lost’  on  your
       system,  or perhaps you were thinking too far ahead and typed the whole
       thing) a ‘/’ or space is added to the end if it isn’t already there.

       Completion works anywhere in the line, not at just the  end;  completed
       text  pushes  the  rest  of  the  line to the right.  Completion in the
       middle of a word often results in leftover characters to the  right  of
       the cursor that need to be deleted.

       Commands  and  variables  can  be  completed in much the same way.  For
       example, typing ‘em[tab]’ would complete ‘em’ to ‘emacs’ if emacs  were
       the  only  command  on your system beginning with ‘em’.  Completion can
       find a command in any directory in path or if given  a  full  pathname.
       Typing  ‘echo  $ar[tab]’  would  complete  ‘$ar’ to ‘$argv’ if no other
       variable began with ‘ar’.

       The shell parses the input buffer to determine  whether  the  word  you
       want  to  complete  should  be  completed  as  a  filename,  command or
       variable.  The first word in the buffer and the  first  word  following
       ‘;’,  ‘|’,  ‘|&’,  ‘&&’  or ‘||’ is considered to be a command.  A word
       beginning with ‘$’ is considered to be a variable.  Anything else is  a
       filename.  An empty line is ‘completed’ as a filename.

       You  can  list the possible completions of a word at any time by typing
       ‘^D’ to run the delete-char-or-list-or-eof editor command.   The  shell
       lists  the  possible  completions  using  the  ls-F builtin (q.v.)  and
       reprints the prompt and unfinished command line, for example:

           > ls /usr/l[^D]
           lbin/       lib/        local/      lost+found/
           > ls /usr/l

       If the autolist shell variable is set, the shell  lists  the  remaining
       choices (if any) whenever completion fails:

           > set autolist
           > nm /usr/lib/libt[tab]
           libtermcap.a@ libtermlib.a@
           > nm /usr/lib/libterm

       If  autolist  is  set  to  ‘ambiguous’,  choices  are  listed only when
       completion  fails  and  adds  no  new  characters  to  the  word  being
       completed.

       A  filename  to be completed can contain variables, your own or others’
       home directories abbreviated with ‘~’ (see Filename  substitution)  and
       directory  stack  entries  abbreviated  with  ‘=’  (see Directory stack
       substitution).  For example,

           > ls ~k[^D]
           kahn    kas     kellogg
           > ls ~ke[tab]
           > ls ~kellogg/

       or

           > set local = /usr/local
           > ls $lo[tab]
           > ls $local/[^D]
           bin/ etc/ lib/ man/ src/
           > ls $local/

       Note that variables can also be expanded explicitly  with  the  expand-
       variables editor command.

       delete-char-or-list-or-eof  lists  at  only the end of the line; in the
       middle of a line it deletes the character under the cursor  and  on  an
       empty  line  it  logs  one  out  or, if ignoreeof is set, does nothing.
       ‘M-^D’, bound to the  editor  command  list-choices,  lists  completion
       possibilities  anywhere  on a line, and list-choices (or any one of the
       related editor commands that do or don’t delete, list and/or  log  out,
       listed  under delete-char-or-list-or-eof) can be bound to ‘^D’ with the
       bindkey builtin command if so desired.

       The complete-word-fwd and complete-word-back editor commands (not bound
       to  any  keys  by default) can be used to cycle up and down through the
       list of possible completions, replacing the current word with the  next
       or previous word in the list.

       The  shell  variable  fignore  can  be  set to a list of suffixes to be
       ignored by completion.  Consider the following:

           > ls
           Makefile        condiments.h~   main.o          side.c
           README          main.c          meal            side.o
           condiments.h    main.c~
           > set fignore = (.o \~)
           > emacs ma[^D]
           main.c   main.c~  main.o
           > emacs ma[tab]
           > emacs main.c

       ‘main.c~’ and ‘main.o’ are ignored by  completion  (but  not  listing),
       because they end in suffixes in fignore.  Note that a ‘\’ was needed in
       front of ‘~’ to prevent it from being expanded  to  home  as  described
       under Filename substitution.  fignore is ignored if only one completion
       is possible.

       If the complete shell variable  is  set  to  ‘enhance’,  completion  1)
       ignores  case  and  2) considers periods, hyphens and underscores (‘.’,
       ‘-’ and ‘_’) to be word separators and hyphens and  underscores  to  be
       equivalent.  If you had the following files

           comp.lang.c      comp.lang.perl   comp.std.c++
           comp.lang.c++    comp.std.c

       and  typed  ‘mail  -f  c.l.c[tab]’,  it  would be completed to ‘mail -f
       comp.lang.c’, and ^D  would  list  ‘comp.lang.c’  and  ‘comp.lang.c++’.
       ‘mail  -f  c..c++[^D]’  would  list ‘comp.lang.c++’ and ‘comp.std.c++’.
       Typing ‘rm a--file[^D]’ in the following directory

           A_silly_file    a-hyphenated-file    another_silly_file

       would list all three files, because case is  ignored  and  hyphens  and
       underscores  are  equivalent.   Periods, however, are not equivalent to
       hyphens or underscores.

       Completion and listing are affected by several other  shell  variables:
       recexact  can be set to complete on the shortest possible unique match,
       even if more typing might result in a longer match:

           > ls
           fodder   foo      food     foonly
           > set recexact
           > rm fo[tab]

       just beeps, because ‘fo’ could expand to ‘fod’ or ‘foo’, but if we type
       another ‘o’,

           > rm foo[tab]
           > rm foo

       the completion completes on ‘foo’, even though ‘food’ and ‘foonly’ also
       match.  autoexpand can be set to run the expand-history editor  command
       before  each  completion  attempt,  autocorrect can be set to spelling-
       correct the word to be completed (see Spelling correction) before  each
       completion  attempt  and  correct  can  be  set  to  complete  commands
       automatically after one hits ‘return’.  matchbeep can be  set  to  make
       completion  beep or not beep in a variety of situations, and nobeep can
       be set to never  beep  at  all.   nostat  can  be  set  to  a  list  of
       directories  and/or  patterns  that  match  directories  to prevent the
       completion mechanism from stat(2)ing those  directories.   listmax  and
       listmaxrows  can  be  set  to  limit  the  number  of  items  and  rows
       (respectively)    that    are    listed    without    asking     first.
       recognize_only_executables  can  be  set  to  make  the shell list only
       executables when listing commands, but it is quite slow.

       Finally, the complete builtin command can be used to tell the shell how
       to  complete  words  other  than  filenames,  commands  and  variables.
       Completion and listing do  not  work  on  glob-patterns  (see  Filename
       substitution),  but  the  list-glob  and  expand-glob  editor  commands
       perform equivalent functions for glob-patterns.

   Spelling correction (+)
       The shell can sometimes correct the spelling of filenames, commands and
       variable names as well as completing and listing them.

       Individual  words  can be spelling-corrected with the spell-word editor
       command (usually bound to M-s and M-S) and the entire input buffer with
       spell-line  (usually  bound to M-$).  The correct shell variable can be
       set to ‘cmd’ to correct the command name or ‘all’ to correct the entire
       line  each  time return is typed, and autocorrect can be set to correct
       the word to be completed before each completion attempt.

       When spelling correction is invoked in any of these ways and the  shell
       thinks that any part of the command line is misspelled, it prompts with
       the corrected line:

           > set correct = cmd
           > lz /usr/bin
           CORRECT>ls /usr/bin (y|n|e|a)?

       One can answer ‘y’ or space to execute the corrected line, ‘e’ to leave
       the  uncorrected  command in the input buffer, ‘a’ to abort the command
       as if ‘^C’ had been hit, and anything else to execute the original line
       unchanged.

       Spelling   correction  recognizes  user-defined  completions  (see  the
       complete builtin command).  If an input word in a position for which  a
       completion is defined resembles a word in the completion list, spelling
       correction registers a misspelling and suggests the latter  word  as  a
       correction.   However,  if  the  input  word  does not match any of the
       possible completions for that position, spelling  correction  does  not
       register a misspelling.

       Like  completion,  spelling  correction  works  anywhere  in  the line,
       pushing the rest of the line to the right and  possibly  leaving  extra
       characters to the right of the cursor.

       Beware:  spelling  correction  is  not  guaranteed  to work the way one
       intends,  and  is  provided  mostly   as   an   experimental   feature.
       Suggestions and improvements are welcome.

   Editor commands (+)
       ‘bindkey’  lists  key  bindings  and  ‘bindkey  -l’  lists  and briefly
       describes editor commands.  Only new or especially  interesting  editor
       commands  are  described here.  See emacs(1) and vi(1) for descriptions
       of each editor’s key bindings.

       The character or characters to which each command is bound  by  default
       is  given  in  parentheses.  ‘^character’ means a control character and
       ‘M-character’ a meta character, typed as escape-character on  terminals
       without  a  meta  key.   Case  counts,  but  commands that are bound to
       letters by default are bound to both lower- and uppercase  letters  for
       convenience.

       complete-word (tab)
               Completes a word as described under Completion and listing.

       complete-word-back (not bound)
               Like  complete-word-fwd, but steps up from the end of the list.

       complete-word-fwd (not bound)
               Replaces the current word with the first word in  the  list  of
               possible completions.  May be repeated to step down through the
               list.  At the end  of  the  list,  beeps  and  reverts  to  the
               incomplete word.

       complete-word-raw (^X-tab)
               Like complete-word, but ignores user-defined completions.

       copy-prev-word (M-^_)
               Copies  the  previous  word  in the current line into the input
               buffer.  See also insert-last-word.

       dabbrev-expand (M-/)
               Expands the current word to the most recent preceding  one  for
               which  the  current is a leading substring, wrapping around the
               history list (once)  if  necessary.   Repeating  dabbrev-expand
               without  any  intervening  typing  changes to the next previous
               word etc., skipping identical matches much like history-search-
               backward does.

       delete-char (bound to ‘Del’ if using the standard /etc/csh.cshrc)
               Deletes  the character under the cursor.  See also delete-char-
               or-list-or-eof.

       delete-char-or-eof (not bound)
               Does delete-char if there is a character under  the  cursor  or
               end-of-file on an empty line.  See also delete-char-or-list-or-
               eof.

       delete-char-or-list (not bound)
               Does delete-char if there is a character under  the  cursor  or
               list-choices  at the end of the line.  See also delete-char-or-
               list-or-eof.

       delete-char-or-list-or-eof (^D)
               Does delete-char if there is  a  character  under  the  cursor,
               list-choices  at the end of the line or end-of-file on an empty
               line.  See also those three commands, each of which does only a
               single  action, and delete-char-or-eof, delete-char-or-list and
               list-or-eof, each of which does a  different  two  out  of  the
               three.

       down-history (down-arrow, ^N)
               Like up-history, but steps down, stopping at the original input
               line.

       end-of-file (not bound)
               Signals an end of file, causing the shell to  exit  unless  the
               ignoreeof  shell  variable  (q.v.) is set to prevent this.  See
               also delete-char-or-list-or-eof.

       expand-history (M-space)
               Expands history substitutions in the current word.  See History
               substitution.  See also magic-space, toggle-literal-history and
               the autoexpand shell variable.

       expand-glob (^X-*)
               Expands the glob-pattern  to  the  left  of  the  cursor.   See
               Filename substitution.

       expand-line (not bound)
               Like  expand-history, but expands history substitutions in each
               word in the input buffer,

       expand-variables (^X-$)
               Expands the variable to the left of the cursor.   See  Variable
               substitution.

       history-search-backward (M-p, M-P)
               Searches  backwards  through  the  history  list  for a command
               beginning with the current contents of the input buffer  up  to
               the  cursor  and  copies  it into the input buffer.  The search
               string  may  be  a  glob-pattern  (see  Filename  substitution)
               containing ‘*’, ‘?’, ‘[]’ or ‘{}’.  up-history and down-history
               will proceed from the appropriate point in  the  history  list.
               Emacs mode only.  See also history-search-forward and i-search-
               back.

       history-search-forward (M-n, M-N)
               Like history-search-backward, but searches forward.

       i-search-back (not bound)
               Searches  backward  like  history-search-backward,  copies  the
               first match into the input buffer with the cursor positioned at
               the end of the pattern, and prompts with ‘bck: ’ and the  first
               match.   Additional  characters  may  be  typed  to  extend the
               search, i-search-back may be typed to continue  searching  with
               the   same   pattern,  wrapping  around  the  history  list  if
               necessary, (i-search-back must be bound to a  single  character
               for  this  to  work) or one of the following special characters
               may be typed:

                   ^W      Appends the rest of the word under  the  cursor  to
                           the search pattern.
                   delete (or any character bound to backward-delete-char)
                           Undoes  the  effect of the last character typed and
                           deletes a character  from  the  search  pattern  if
                           appropriate.
                   ^G      If  the  previous search was successful, aborts the
                           entire search.  If  not,  goes  back  to  the  last
                           successful search.
                   escape  Ends  the  search,  leaving the current line in the
                           input buffer.

               Any other character not bound to self-insert-command terminates
               the  search,  leaving the current line in the input buffer, and
               is then interpreted as normal input.  In particular, a carriage
               return  causes  the  current  line  to be executed.  Emacs mode
               only.  See also i-search-fwd and history-search-backward.

       i-search-fwd (not bound)
               Like i-search-back, but searches forward.

       insert-last-word (M-_)
               Inserts the last word of the previous input  line  (‘!$’)  into
               the input buffer.  See also copy-prev-word.

       list-choices (M-^D)
               Lists  completion  possibilities  as described under Completion
               and listing.  See  also  delete-char-or-list-or-eof  and  list-
               choices-raw.

       list-choices-raw (^X-^D)
               Like list-choices, but ignores user-defined completions.

       list-glob (^X-g, ^X-G)
               Lists  (via  the ls-F builtin) matches to the glob-pattern (see
               Filename substitution) to the left of the cursor.

       list-or-eof (not bound)
               Does list-choices or end-of-file on an empty  line.   See  also
               delete-char-or-list-or-eof.

       magic-space (not bound)
               Expands history substitutions in the current line, like expand-
               history, and inserts a space.  magic-space is  designed  to  be
               bound to the space bar, but is not bound by default.

       normalize-command (^X-?)
               Searches  for  the  current  word  in PATH and, if it is found,
               replaces it with the full  path  to  the  executable.   Special
               characters  are  quoted.   Aliases  are expanded and quoted but
               commands within aliases are not.  This command is  useful  with
               commands  that  take commands as arguments, e.g., ‘dbx’ and ‘sh
               -x’.

       normalize-path (^X-n, ^X-N)
               Expands the  current  word  as  described  under  the  ‘expand’
               setting of the symlinks shell variable.

       overwrite-mode (unbound)
               Toggles between input and overwrite modes.

       run-fg-editor (M-^Z)
               Saves the current input line and looks for a stopped job with a
               name equal to the last component of the file name part  of  the
               EDITOR  or VISUAL environment variables, or, if neither is set,
               ‘ed’ or ‘vi’.  If such a job is found, it is  restarted  as  if
               ‘fg  %job’  had  been  typed.   This is used to toggle back and
               forth between an editor and the shell easily.  Some people bind
               this command to ‘^Z’ so they can do this even more easily.

       run-help (M-h, M-H)
               Searches  for  documentation  on the current command, using the
               same notion of ‘current command’ as  the  completion  routines,
               and  prints  it.   There  is no way to use a pager; run-help is
               designed  for  short  help  files.   If   the   special   alias
               helpcommand  is  defined,  it is run with the command name as a
               sole argument.  Else, documentation should be in a  file  named
               command.help, command.1, command.6, command.8 or command, which
               should be in  one  of  the  directories  listed  in  the  HPATH
               environment variable.  If there is more than one help file only
               the first is printed.

       self-insert-command (text characters)
               In insert mode (the default), inserts the typed character  into
               the  input  line  after  the  character  under  the cursor.  In
               overwrite mode, replaces the character under  the  cursor  with
               the  typed  character.   The  input  mode is normally preserved
               between lines, but the inputmode shell variable can be  set  to
               ‘insert’  or  ‘overwrite’ to put the editor in that mode at the
               beginning of each line.  See also overwrite-mode.

       sequence-lead-in (arrow prefix, meta prefix, ^X)
               Indicates that the following characters are part of a multi-key
               sequence.   Binding  a  command  to a multi-key sequence really
               creates two bindings: the first character  to  sequence-lead-in
               and the whole sequence to the command.  All sequences beginning
               with a character  bound  to  sequence-lead-in  are  effectively
               bound to undefined-key unless bound to another command.

       spell-line (M-$)
               Attempts  to  correct  the  spelling  of each word in the input
               buffer,  like  spell-word,  but  ignores  words   whose   first
               character is one of ‘-’, ‘!’, ‘^’ or ‘%’, or which contain ‘\’,
               ‘*’ or ‘?’, to avoid problems with switches, substitutions  and
               the like.  See Spelling correction.

       spell-word (M-s, M-S)
               Attempts  to  correct  the  spelling  of  the  current  word as
               described under Spelling correction.  Checks each component  of
               a word which appears to be a pathname.

       toggle-literal-history (M-r, M-R)
               Expands  or  ‘unexpands’  history  substitutions  in  the input
               buffer.  See  also  expand-history  and  the  autoexpand  shell
               variable.

       undefined-key (any unbound key)
               Beeps.

       up-history (up-arrow, ^P)
               Copies  the  previous  entry in the history list into the input
               buffer.  If histlit is set, uses the literal form of the entry.
               May  be  repeated to step up through the history list, stopping
               at the top.

       vi-search-back (?)
               Prompts with ‘?’ for a search string  (which  may  be  a  glob-
               pattern,  as with history-search-backward), searches for it and
               copies it into the input buffer.  The bell rings if no match is
               found.   Hitting  return  ends  the  search and leaves the last
               match in the input buffer.  Hitting escape ends the search  and
               executes the match.  vi mode only.

       vi-search-fwd (/)
               Like vi-search-back, but searches forward.

       which-command (M-?)
               Does  a  which  (see the description of the builtin command) on
               the first word of the input buffer.

       yank-pop (M-y)
               When executed immediately after a  yank  or  another  yank-pop,
               replaces  the  yanked string with the next previous string from
               the  killring.  This  also  has  the  effect  of  rotating  the
               killring,  such  that  this  string will be considered the most
               recently killed by a later  yank  command.  Repeating  yank-pop
               will cycle through the killring any number of times.

   Lexical structure
       The  shell  splits  input  lines  into  words  at blanks and tabs.  The
       special characters ‘&’, ‘|’, ‘;’,  ‘<’,  ‘>’,  ‘(’,  and  ‘)’  and  the
       doubled characters ‘&&’, ‘||’, ‘<<’ and ‘>>’ are always separate words,
       whether or not they are surrounded by whitespace.

       When the shell’s input is not a terminal, the character ‘#’ is taken to
       begin  a  comment.  Each ‘#’ and the rest of the input line on which it
       appears is discarded before further parsing.

       A special character (including a blank or tab) may  be  prevented  from
       having  its special meaning, and possibly made part of another word, by
       preceding it with a backslash (‘\’) or enclosing it  in  single  (‘’’),
       double  (‘"’)  or  backward  (‘‘’) quotes.  When not otherwise quoted a
       newline preceded by a ‘\’ is equivalent to a blank, but  inside  quotes
       this sequence results in a newline.

       Furthermore,  all Substitutions (see below) except History substitution
       can be prevented by enclosing the strings  (or  parts  of  strings)  in
       which  they  appear  with  single  quotes  or  by  quoting  the crucial
       character(s) (e.g., ‘$’ or ‘‘’ for  Variable  substitution  or  Command
       substitution   respectively)  with  ‘\’.   (Alias  substitution  is  no
       exception: quoting in any way any character of  a  word  for  which  an
       alias  has  been defined prevents substitution of the alias.  The usual
       way of quoting an alias is to precede it  with  a  backslash.)  History
       substitution  is  prevented  by  backslashes  but not by single quotes.
       Strings  quoted  with  double  or  backward  quotes  undergo   Variable
       substitution  and  Command  substitution,  but  other substitutions are
       prevented.

       Text inside single or double quotes becomes a single word (or  part  of
       one).   Metacharacters  in these strings, including blanks and tabs, do
       not form separate  words.   Only  in  one  special  case  (see  Command
       substitution below) can a double-quoted string yield parts of more than
       one word; single-quoted strings never do.  Backward quotes are special:
       they  signal Command substitution (q.v.), which may result in more than
       one word.

       Quoting complex strings, particularly strings which themselves  contain
       quoting characters, can be confusing.  Remember that quotes need not be
       used as they are in human writing!  It may be easier to  quote  not  an
       entire  string,  but only those parts of the string which need quoting,
       using different types of quoting to do so if appropriate.

       The  backslash_quote  shell  variable  (q.v.)  can  be  set   to   make
       backslashes  always quote ‘\’, ‘’’, and ‘"’.  (+) This may make complex
       quoting tasks easier, but it can cause syntax errors in csh(1) scripts.

   Substitutions
       We  now  describe the various transformations the shell performs on the
       input in the order in which they occur.  We note in  passing  the  data
       structures  involved  and the commands and variables which affect them.
       Remember that substitutions can be prevented by  quoting  as  described
       under Lexical structure.

   History substitution
       Each  command,  or  ‘‘event’’,  input from the terminal is saved in the
       history list.  The previous command is always saved,  and  the  history
       shell  variable can be set to a number to save that many commands.  The
       histdup shell variable can be set  to  not  save  duplicate  events  or
       consecutive duplicate events.

       Saved  commands  are  numbered sequentially from 1 and stamped with the
       time.  It is not usually  necessary  to  use  event  numbers,  but  the
       current  event  number can be made part of the prompt by placing an ‘!’
       in the prompt shell variable.

       The shell actually saves history in expanded and  literal  (unexpanded)
       forms.  If the histlit shell variable is set, commands that display and
       store history use the literal form.

       The history builtin command can print, store in  a  file,  restore  and
       clear the history list at any time, and the savehist and histfile shell
       variables can be can be set to store the history list automatically  on
       logout and restore it on login.

       History  substitutions  introduce  words from the history list into the
       input stream, making it easy to repeat commands, repeat arguments of  a
       previous  command  in  the current command, or fix spelling mistakes in
       the  previous  command  with  little  typing  and  a  high  degree   of
       confidence.

       History  substitutions  begin  with  the character ‘!’.  They may begin
       anywhere in the input stream, but they do not nest.   The  ‘!’  may  be
       preceded  by  a  ‘\’ to prevent its special meaning; for convenience, a
       ‘!’ is passed unchanged when it is followed by a blank,  tab,  newline,
       ‘=’ or ‘(’.  History substitutions also occur when an input line begins
       with ‘^’.  This special abbreviation  will  be  described  later.   The
       characters  used  to  signal  history substitution (‘!’ and ‘^’) can be
       changed by setting the histchars shell variable.  Any input line  which
       contains a history substitution is printed before it is executed.

       A  history  substitution  may  have  an  ‘‘event specification’’, which
       indicates the event  from  which  words  are  to  be  taken,  a  ‘‘word
       designator’’,  which  selects  particular  words from the chosen event,
       and/or a ‘‘modifier’’, which manipulates the selected words.

       An event specification can be

           n       A number, referring to a particular event
           -n      An offset, referring to the  event  n  before  the  current
                   event
           #       The  current  event.   This  should  be  used  carefully in
                   csh(1), where there is no check for recursion.  tcsh allows
                   10 levels of recursion.  (+)
           !       The previous event (equivalent to ‘-1’)
           s       The  most  recent  event  whose  first word begins with the
                   string s
           ?s?     The most recent event which contains  the  string  s.   The
                   second  ‘?’ can be omitted if it is immediately followed by
                   a newline.

       For example, consider this bit of someone’s history list:

            9  8:30    nroff -man wumpus.man
           10  8:31    cp wumpus.man wumpus.man.old
           11  8:36    vi wumpus.man
           12  8:37    diff wumpus.man.old wumpus.man

       The commands are shown with their event numbers and time  stamps.   The
       current  event,  which we haven’t typed in yet, is event 13.  ‘!11’ and
       ‘!-2’ refer to event 11.  ‘!!’ refers to the previous event, 12.   ‘!!’
       can  be  abbreviated  ‘!’  if  it  is followed by ‘:’ (‘:’ is described
       below).  ‘!n’ refers to event 9, which begins with ‘n’.  ‘!?old?’  also
       refers  to event 12, which contains ‘old’.  Without word designators or
       modifiers history references simply expand to the entire event,  so  we
       might  type  ‘!cp’  to redo the copy command or ‘!!|more’ if the ‘diff’
       output scrolled off the top of the screen.

       History references may be insulated  from  the  surrounding  text  with
       braces  if  necessary.   For  example, ‘!vdoc’ would look for a command
       beginning with  ‘vdoc’,  and,  in  this  example,  not  find  one,  but
       ‘!{v}doc’  would  expand  unambiguously to ‘vi wumpus.mandoc’.  Even in
       braces, history substitutions do not nest.

       (+) While csh(1) expands, for example, ‘!3d’ to event 3 with the letter
       ‘d’  appended  to  it, tcsh expands it to the last event beginning with
       ‘3d’; only completely numeric arguments are treated as  event  numbers.
       This  makes  it  possible  to recall events beginning with numbers.  To
       expand ‘!3d’ as in csh(1) say ‘!\3d’.

       To select words from an event we can follow the event specification  by
       a  ‘:’  and  a designator for the desired words.  The words of an input
       line are numbered from 0, the first (usually command) word being 0, the
       second  word (first argument) being 1, etc.  The basic word designators
       are:

           0       The first (command) word
           n       The nth argument
           ^       The first argument, equivalent to ‘1’
           $       The last argument
           %       The word matched by an ?s? search
           x-y     A range of words
           -y      Equivalent to 0-y
           *       Equivalent to ‘^-$’,  but  returns  nothing  if  the  event
                   contains only 1 word
           x*      Equivalent to x-$
           x-      Equivalent to x*, but omitting the last word (‘$’)

       Selected  words  are inserted into the command line separated by single
       blanks.  For example, the ‘diff’ command in the previous example  might
       have been typed as ‘diff !!:1.old !!:1’ (using ‘:1’ to select the first
       argument from the previous event) or ‘diff !-2:2 !-2:1’ to  select  and
       swap  the arguments from the ‘cp’ command.  If we didn’t care about the
       order of the ‘diff’ we might have said ‘diff !-2:1-2’ or  simply  ‘diff
       !-2:*’.   The  ‘cp’  command  might  have  been  written ‘cp wumpus.man
       !#:1.old’, using ‘#’ to refer to the current event.  ‘!n:-  hurkle.man’
       would  reuse the first two words from the ‘nroff’ command to say ‘nroff
       -man hurkle.man’.

       The ‘:’ separating the event specification from the word designator can
       be omitted if the argument selector begins with a ‘^’, ‘$’, ‘*’, ‘%’ or
       ‘-’.  For example, our ‘diff’ command might  have  been  ‘diff  !!^.old
       !!^’  or,  equivalently,  ‘diff  !!$.old  !!$’.   However,  if  ‘!!’ is
       abbreviated ‘!’, an  argument  selector  beginning  with  ‘-’  will  be
       interpreted as an event specification.

       A   history   reference  may  have  a  word  designator  but  no  event
       specification.  It then references the  previous  command.   Continuing
       our  ‘diff’  example, we could have said simply ‘diff !^.old !^’ or, to
       get the arguments in the opposite order, just ‘diff !*’.

       The  word  or  words  in  a  history  reference  can  be   edited,   or
       ‘‘modified’’, by following it with one or more modifiers, each preceded
       by a ‘:’:

           h       Remove a trailing pathname component, leaving the head.
           t       Remove all leading pathname components, leaving the tail.
           r       Remove a filename extension ‘.xxx’, leaving the root  name.
           e       Remove all but the extension.
           u       Uppercase the first lowercase letter.
           l       Lowercase the first uppercase letter.
           s/l/r/  Substitute  l  for  r.   l is simply a string like r, not a
                   regular expression as in the eponymous ed(1) command.   Any
                   character  may  be used as the delimiter in place of ‘/’; a
                   ‘\’ can be used to quote the delimiter inside l and r.  The
                   character  ‘&’  in  the r is replaced by l; ‘\’ also quotes
                   ‘&’.   If  l  is  empty  (‘‘’’),  the  l  from  a  previous
                   substitution   or   the  s  from  a  previous  ‘?s?’  event
                   specification is  used.   The  trailing  delimiter  may  be
                   omitted if it is immediately followed by a newline.
           &       Repeat the previous substitution.
           g       Apply the following modifier once to each word.
           a (+)   Apply the following modifier as many times as possible to a
                   single word.  ‘a’ and ‘g’ can be used together to  apply  a
                   modifier  globally.   In  the current implementation, using
                   the ‘a’ and ‘s’ modifiers together can lead to an  infinite
                   loop.  For example, ‘:as/f/ff/’ will never terminate.  This
                   behavior might change in the future.
           p       Print the new command line but do not execute it.
           q       Quote   the   substituted   words,    preventing    further
                   substitutions.
           x       Like  q, but break into words at blanks, tabs and newlines.

       Modifiers are applied to only the first modifiable word (unless ‘g’  is
       used).  It is an error for no word to be modifiable.

       For  example,  the  ‘diff’  command  might  have  been written as ‘diff
       wumpus.man.old !#^:r’, using ‘:r’  to  remove  ‘.old’  from  the  first
       argument  on  the  same  line  (‘!#^’).   We  could say ‘echo hello out
       there’, then ‘echo !*:u’ to capitalize ‘hello’, ‘echo !*:au’ to say  it
       out  loud,  or ‘echo !*:agu’ to really shout.  We might follow ‘mail -s
       "I forgot my password" rot’ with ‘!:s/rot/root’ to correct the spelling
       of ‘root’ (but see Spelling correction for a different approach).

       There is a special abbreviation for substitutions.  ‘^’, when it is the
       first character on an input line, is equivalent  to  ‘!:s^’.   Thus  we
       might  have  said  ‘^rot^root’  to  make the spelling correction in the
       previous example.  This is the only history substitution which does not
       explicitly begin with ‘!’.

       (+) In csh as such, only one modifier may be applied to each history or
       variable expansion.  In tcsh, more than one may be used, for example

           % mv wumpus.man /usr/man/man1/wumpus.1
           % man !$:t:r
           man wumpus

       In csh, the result would be ‘wumpus.1:r’.  A substitution followed by a
       colon may need to be insulated from it with braces:

           > mv a.out /usr/games/wumpus
           > setenv PATH !$:h:$PATH
           Bad ! modifier: $.
           > setenv PATH !{-2$:h}:$PATH
           setenv PATH /usr/games:/bin:/usr/bin:.

       The  first attempt would succeed in csh but fails in tcsh, because tcsh
       expects another modifier after the second colon rather than ‘$’.

       Finally, history can be accessed through the editor as well as  through
       the  substitutions  just described.  The up- and down-history, history-
       search-backward and -forward, i-search-back  and  -fwd,  vi-search-back
       and  -fwd,  copy-prev-word  and insert-last-word editor commands search
       for events in the history list and copy them  into  the  input  buffer.
       The toggle-literal-history editor command switches between the expanded
       and literal forms of history lines in the input buffer.  expand-history
       and expand-line expand history substitutions in the current word and in
       the entire input buffer respectively.

   Alias substitution
       The shell maintains a list of aliases  which  can  be  set,  unset  and
       printed  by  the  alias  and unalias commands.  After a command line is
       parsed into simple commands (see  Commands)  the  first  word  of  each
       command,  left-to-right,  is checked to see if it has an alias.  If so,
       the first word is replaced by the  alias.   If  the  alias  contains  a
       history  reference,  it undergoes History substitution (q.v.) as though
       the original command were the previous input line.  If the  alias  does
       not contain a history reference, the argument list is left untouched.

       Thus  if  the  alias  for ‘ls’ were ‘ls -l’ the command ‘ls /usr’ would
       become ‘ls -l /usr’, the argument list here being undisturbed.  If  the
       alias  for ‘lookup’ were ‘grep !^ /etc/passwd’ then ‘lookup bill’ would
       become ‘grep bill /etc/passwd’.   Aliases  can  be  used  to  introduce
       parser metasyntax.  For example, ‘alias print ’pr \!* | lpr’’ defines a
       ‘‘command’’ (‘print’) which pr(1)s its arguments to the line printer.

       Alias substitution is repeated until the first word of the command  has
       no  alias.  If an alias substitution does not change the first word (as
       in the previous example) it is flagged to prevent a loop.  Other  loops
       are detected and cause an error.

       Some aliases are referred to by the shell; see Special aliases.

   Variable substitution
       The  shell  maintains a list of variables, each of which has as value a
       list of zero or more words.  The  values  of  shell  variables  can  be
       displayed  and  changed  with  the  set and unset commands.  The system
       maintains its own list of  ‘‘environment’’  variables.   These  can  be
       displayed and changed with printenv, setenv and unsetenv.

       (+)  Variables  may  be  made read-only with ‘set -r’ (q.v.)  Read-only
       variables may not be modified or unset; attempting to do so will  cause
       an  error.  Once made read-only, a variable cannot be made writable, so
       ‘set -r’ should be used with caution.  Environment variables cannot  be
       made read-only.

       Some  variables  are  set  by  the  shell  or  referred  to by it.  For
       instance, the argv variable is an image of the shell’s  argument  list,
       and  words  of  this  variable’s value are referred to in special ways.
       Some of the variables referred to by the shell are toggles;  the  shell
       does  not  care  what their value is, only whether they are set or not.
       For instance, the verbose variable is a  toggle  which  causes  command
       input  to  be  echoed.   The -v command line option sets this variable.
       Special shell variables lists all variables which are  referred  to  by
       the shell.

       Other  operations treat variables numerically.  The ‘@’ command permits
       numeric calculations to be performed  and  the  result  assigned  to  a
       variable.  Variable values are, however, always represented as (zero or
       more) strings.  For the purposes of numeric operations, the null string
       is considered to be zero, and the second and subsequent words of multi-
       word values are ignored.

       After the input line is aliased and parsed, and before each command  is
       executed,  variable  substitution is performed keyed by ‘$’ characters.
       This expansion can be prevented by preceding the ‘$’ with a ‘\’  except
       within  ‘"’s  where  it  always  occurs, and within ‘’’s where it never
       occurs.  Strings quoted by  ‘‘’  are  interpreted  later  (see  Command
       substitution  below)  so  ‘$’  substitution  does not occur there until
       later, if at all.  A ‘$’ is passed unchanged if followed  by  a  blank,
       tab, or end-of-line.

       Input/output redirections are recognized before variable expansion, and
       are variable expanded separately.   Otherwise,  the  command  name  and
       entire  argument  list  are expanded together.  It is thus possible for
       the first (command) word (to this point)  to  generate  more  than  one
       word,  the  first  of  which  becomes the command name, and the rest of
       which become arguments.

       Unless enclosed in ‘"’ or  given  the  ‘:q’  modifier  the  results  of
       variable   substitution   may   eventually   be  command  and  filename
       substituted.  Within ‘"’, a variable whose value consists  of  multiple
       words  expands  to  a (portion of a) single word, with the words of the
       variable’s value separated  by  blanks.   When  the  ‘:q’  modifier  is
       applied  to  a  substitution the variable will expand to multiple words
       with each word separated by a blank and quoted to prevent later command
       or filename substitution.

       The  following  metasequences  are  provided  for  introducing variable
       values into the shell input.  Except  as  noted,  it  is  an  error  to
       reference a variable which is not set.

       $name
       ${name} Substitutes  the  words  of  the  value  of variable name, each
               separated by a blank.   Braces  insulate  name  from  following
               characters   which  would  otherwise  be  part  of  it.   Shell
               variables have names consisting of up to 20 letters and  digits
               starting with a letter.  The underscore character is considered
               a letter.  If name is not a shell variable, but is set  in  the
               environment, then that value is returned (but ‘:’ modifiers and
               the other forms given below are not available in this case).
       $name[selector]
       ${name[selector]}
               Substitutes only the selected words from  the  value  of  name.
               The  selector  is subjected to ‘$’ substitution and may consist
               of a single number or two numbers  separated  by  a  ‘-’.   The
               first word of a variable’s value is numbered ‘1’.  If the first
               number of a range is omitted it defaults to ‘1’.  If  the  last
               member  of  a  range  is  omitted it defaults to ‘$#name’.  The
               selector ‘*’ selects all words.  It is not an error for a range
               to be empty if the second argument is omitted or in range.
       $0      Substitutes  the  name  of the file from which command input is
               being read.  An error occurs if the name is not known.
       $number
       ${number}
               Equivalent to ‘$argv[number]’.
       $*      Equivalent to ‘$argv’, which is equivalent to ‘$argv[*]’.

       The ‘:’ modifiers described  under  History  substitution,  except  for
       ‘:p’,  can be applied to the substitutions above.  More than one may be
       used.  (+) Braces may be needed to  insulate  a  variable  substitution
       from  a  literal  colon  just  as with History substitution (q.v.); any
       modifiers must appear within the braces.

       The following substitutions can not be modified with ‘:’ modifiers.

       $?name
       ${?name}
               Substitutes the string ‘1’ if name is set, ‘0’ if it is not.
       $?0     Substitutes ‘1’ if the current input filename is known, ‘0’  if
               it is not.  Always ‘0’ in interactive shells.
       $#name
       ${#name}
               Substitutes the number of words in name.
       $#      Equivalent to ‘$#argv’.  (+)
       $%name
       ${%name}
               Substitutes the number of characters in name.  (+)
       $%number
       ${%number}
               Substitutes the number of characters in $argv[number].  (+)
       $?      Equivalent to ‘$status’.  (+)
       $$      Substitutes the (decimal) process number of the (parent) shell.
       $!      Substitutes the (decimal) process number of the last background
               process started by this shell.  (+)
       $_      Substitutes the command line of the last command executed.  (+)
       $<      Substitutes a line from the standard  input,  with  no  further
               interpretation  thereafter.   It  can  be used to read from the
               keyboard in a shell script.  (+) While csh always quotes $<, as
               if  it  were equivalent to ‘$<:q’, tcsh does not.  Furthermore,
               when tcsh is waiting for a line to be typed the user  may  type
               an  interrupt  to interrupt the sequence into which the line is
               to be substituted, but csh does not allow this.

       The editor command expand-variables, normally bound to ‘^X-$’,  can  be
       used to interactively expand individual variables.

   Command, filename and directory stack substitution
       The remaining substitutions are applied selectively to the arguments of
       builtin commands.  This means that portions of  expressions  which  are
       not  evaluated  are  not  subjected  to these expansions.  For commands
       which are not internal to the shell, the command  name  is  substituted
       separately from the argument list.  This occurs very late, after input-
       output redirection is performed, and in a child of the main shell.

   Command substitution
       Command substitution is indicated by a command enclosed  in  ‘‘’.   The
       output  from  such  a  command is broken into separate words at blanks,
       tabs and newlines,  and  null  words  are  discarded.   The  output  is
       variable  and  command  substituted  and  put  in place of the original
       string.

       Command substitutions inside double  quotes  (‘"’)  retain  blanks  and
       tabs; only newlines force new words.  The single final newline does not
       force a new word in any case.   It  is  thus  possible  for  a  command
       substitution  to yield only part of a word, even if the command outputs
       a complete line.

       By default, the shell since  version  6.12  replaces  all  newline  and
       carriage  return  characters  in  the  command  by  spaces.  If this is
       switched off by unsetting csubstnonl,  newlines  separate  commands  as
       usual.

   Filename substitution
       If a word contains any of the characters ‘*’, ‘?’, ‘[’ or ‘{’ or begins
       with the character ‘~’ it is a  candidate  for  filename  substitution,
       also  known  as  ‘‘globbing’’.  This word is then regarded as a pattern
       (‘‘glob-pattern’’), and replaced with an alphabetically sorted list  of
       file names which match the pattern.

       In matching filenames, the character ‘.’ at the beginning of a filename
       or immediately following a ‘/’, as well as the character  ‘/’  must  be
       matched   explicitly.    The   character  ‘*’  matches  any  string  of
       characters, including the null string.  The character ‘?’  matches  any
       single  character.   The  sequence  ‘[...]’  matches  any  one  of  the
       characters enclosed.  Within ‘[...]’, a pair of characters separated by
       ‘-’ matches any character lexically between the two.

       (+)  Some  glob-patterns  can be negated: The sequence ‘[^...]’ matches
       any single character not specified by the characters and/or  ranges  of
       characters in the braces.

       An entire glob-pattern can also be negated with ‘^’:

           > echo *
           bang crash crunch ouch
           > echo ^cr*
           bang ouch

       Glob-patterns  which  do not use ‘?’, ‘*’, or ‘[]’ or which use ‘{}’ or
       ‘~’ (below) are not negated correctly.

       The metanotation ‘a{b,c,d}e’ is a shorthand for ‘abe ace  ade’.   Left-
       to-right  order  is preserved: ‘/usr/source/s1/{oldls,ls}.c’ expands to
       ‘/usr/source/s1/oldls.c /usr/source/s1/ls.c’.  The results  of  matches
       are   sorted  separately  at  a  low  level  to  preserve  this  order:
       ‘../{memo,*box}’ might expand to ‘../memo ../box ../mbox’.  (Note  that
       ‘memo’  was not sorted with the results of matching ‘*box’.)  It is not
       an error when this construct expands to files which do not  exist,  but
       it  is  possible  to  get an error from a command to which the expanded
       list is passed.  This construct may be nested.  As a special  case  the
       words ‘{’, ‘}’ and ‘{}’ are passed undisturbed.

       The  character  ‘~’  at  the  beginning  of  a  filename refers to home
       directories.  Standing alone, i.e., ‘~’, it expands  to  the  invoker’s
       home  directory  as  reflected in the value of the home shell variable.
       When  followed  by  a  name  consisting  of  letters,  digits  and  ‘-’
       characters the shell searches for a user with that name and substitutes
       their home directory;  thus  ‘~ken’  might  expand  to  ‘/usr/ken’  and
       ‘~ken/chmach’  to  ‘/usr/ken/chmach’.  If the character ‘~’ is followed
       by a character other than a letter or ‘/’ or appears elsewhere than  at
       the  beginning  of  a  word,  it  is  left undisturbed.  A command like
       ‘setenv MANPATH /usr/man:/usr/local/man:~/lib/man’ does not, therefore,
       do home directory substitution as one might hope.

       It is an error for a glob-pattern containing ‘*’, ‘?’, ‘[’ or ‘~’, with
       or without ‘^’, not to match any files.  However, only one pattern in a
       list  of  glob-patterns  must  match a file (so that, e.g., ‘rm *.a *.c
       *.o’ would fail only if there were no files in  the  current  directory
       ending  in ‘.a’, ‘.c’, or ‘.o’), and if the nonomatch shell variable is
       set a pattern (or list of  patterns)  which  matches  nothing  is  left
       unchanged rather than causing an error.

       The  noglob shell variable can be set to prevent filename substitution,
       and the expand-glob editor command, normally bound to  ‘^X-*’,  can  be
       used to interactively expand individual filename substitutions.

   Directory stack substitution (+)
       The  directory stack is a list of directories, numbered from zero, used
       by the pushd, popd and dirs builtin commands (q.v.).  dirs  can  print,
       store in a file, restore and clear the directory stack at any time, and
       the savedirs and dirsfile shell variables  can  be  set  to  store  the
       directory  stack  automatically on logout and restore it on login.  The
       dirstack shell variable can be examined to see the directory stack  and
       set to put arbitrary directories into the directory stack.

       The character ‘=’ followed by one or more digits expands to an entry in
       the directory stack.   The  special  case  ‘=-’  expands  to  the  last
       directory in the stack.  For example,

           > dirs -v
           0       /usr/bin
           1       /usr/spool/uucp
           2       /usr/accts/sys
           > echo =1
           /usr/spool/uucp
           > echo =0/calendar
           /usr/bin/calendar
           > echo =-
           /usr/accts/sys

       The  noglob  and  nonomatch  shell variables and the expand-glob editor
       command apply to directory stack as well as filename substitutions.

   Other substitutions (+)
       There  are  several  more  transformations  involving  filenames,   not
       strictly related to the above but mentioned here for completeness.  Any
       filename may be expanded to a full  path  when  the  symlinks  variable
       (q.v.)  is  set  to ‘expand’.  Quoting prevents this expansion, and the
       normalize-path editor command does it on demand.  The normalize-command
       editor  command  expands  commands  in  PATH into full paths on demand.
       Finally, cd and pushd  interpret  ‘-’  as  the  old  working  directory
       (equivalent  to the shell variable owd).  This is not a substitution at
       all,  but  an  abbreviation  recognized   by   only   those   commands.
       Nonetheless, it too can be prevented by quoting.

   Commands
       The  next  three  sections describe how the shell executes commands and
       deals with their input and output.

   Simple commands, pipelines and sequences
       A simple command is a sequence of words, the first of  which  specifies
       the  command to be executed.  A series of simple commands joined by ‘|’
       characters forms a pipeline.  The output of each command in a  pipeline
       is connected to the input of the next.

       Simple  commands  and  pipelines may be joined into sequences with ‘;’,
       and will be executed sequentially.  Commands and pipelines can also  be
       joined  into  sequences  with  ‘||’  or  ‘&&’,  indicating, as in the C
       language, that the second is to be executed only if the first fails  or
       succeeds respectively.

       A  simple  command,  pipeline or sequence may be placed in parentheses,
       ‘()’, to form a simple command, which may in turn be a component  of  a
       pipeline  or sequence.  A command, pipeline or sequence can be executed
       without waiting for it to terminate by following it with an ‘&’.

   Builtin and non-builtin command execution
       Builtin commands are executed within the shell.  If any component of  a
       pipeline except the last is a builtin command, the pipeline is executed
       in a subshell.

       Parenthesized commands are always executed in a subshell.

           (cd; pwd); pwd

       thus prints the home directory, leaving you where  you  were  (printing
       this after the home directory), while

           cd; pwd

       leaves  you  in  the  home  directory.  Parenthesized commands are most
       often used to prevent cd from affecting the current shell.

       When a command to be executed is found not to be a builtin command  the
       shell  attempts to execute the command via execve(2).  Each word in the
       variable path names a directory in which the shell will  look  for  the
       command.  If it is given neither a -c nor a -t option, the shell hashes
       the names in these directories into an internal table so that  it  will
       try  an execve(2) in only a directory where there is a possibility that
       the command resides there.  This greatly speeds command location when a
       large  number  of  directories are present in the search path.  If this
       mechanism has been turned off (via unhash), if the shell was given a -c
       or  -t  argument  or  in  any case for each directory component of path
       which does not begin with a ‘/’, the  shell  concatenates  the  current
       working  directory with the given command name to form a path name of a
       file which it then attempts to execute.

       If the file has execute permissions but is not  an  executable  to  the
       system  (i.e.,  it  is  neither  an executable binary nor a script that
       specifies its interpreter), then it is assumed to be a file  containing
       shell  commands  and  a  new  shell  is  spawned to read it.  The shell
       special alias may be set to specify an interpreter other than the shell
       itself.

       On  systems  which  do  not  understand  the  ‘#!’  script  interpreter
       convention the shell may be compiled to emulate  it;  see  the  version
       shell  variable.  If so, the shell checks the first line of the file to
       see if it is of the form ‘#!interpreter arg ...’.  If it is, the  shell
       starts  interpreter  with  the  given  args and feeds the file to it on
       standard input.

   Input/output
       The standard input and standard output of a command may  be  redirected
       with the following syntax:

       < name  Open  file  name (which is first variable, command and filename
               expanded) as the standard input.
       << word Read the shell input up to a line which is identical  to  word.
               word   is  not  subjected  to  variable,  filename  or  command
               substitution, and each input line is compared  to  word  before
               any  substitutions  are  done  on  this  input  line.  Unless a
               quoting ‘\’, ‘"’, ‘’  or  ‘‘’  appears  in  word  variable  and
               command  substitution  is  performed  on the intervening lines,
               allowing ‘\’ to quote ‘$’, ‘\’ and  ‘‘’.   Commands  which  are
               substituted  have  all  blanks,  tabs,  and newlines preserved,
               except for the final newline which is dropped.   The  resultant
               text is placed in an anonymous temporary file which is given to
               the command as standard input.
       > name
       >! name
       >& name
       >&! name
               The file name is used as standard output.  If the file does not
               exist  then it is created; if the file exists, it is truncated,
               its previous contents being lost.

               If the shell variable noclobber is set, then the file must  not
               exist  or  be  a  character  special  file (e.g., a terminal or
               ‘/dev/null’)  or  an  error  results.    This   helps   prevent
               accidental  destruction  of  files.  In this case the ‘!’ forms
               can be used to suppress this check.

               The forms involving ‘&’ route the diagnostic  output  into  the
               specified  file  as  well  as  the  standard  output.   name is
               expanded in the same way as ‘<’ input filenames are.
       >> name
       >>& name
       >>! name
       >>&! name
               Like ‘>’, but appends output to the end of name.  If the  shell
               variable noclobber is set, then it is an error for the file not
               to exist, unless one of the ‘!’ forms is given.

       A command receives the environment in which the shell  was  invoked  as
       modified by the input-output parameters and the presence of the command
       in a pipeline.  Thus, unlike some previous shells, commands run from  a
       file  of  shell  commands have no access to the text of the commands by
       default; rather they receive the original standard input of the  shell.
       The ‘<<’ mechanism should be used to present inline data.  This permits
       shell command scripts to function as components of pipelines and allows
       the  shell  to  block  read  its input.  Note that the default standard
       input for a command run detached is not the empty file  /dev/null,  but
       the original standard input of the shell.  If this is a terminal and if
       the process attempts to read from the terminal, then the  process  will
       block and the user will be notified (see Jobs).

       Diagnostic  output  may  be  directed  through a pipe with the standard
       output.  Simply use the form ‘|&’ rather than just ‘|’.

       The shell cannot presently  redirect  diagnostic  output  without  also
       redirecting  standard  output,  but  ‘(command > output-file) >& error-
       file’ is often an acceptable workaround.  Either output-file or  error-
       file may be ‘/dev/tty’ to send output to the terminal.

   Features
       Having  described  how  the  shell accepts, parses and executes command
       lines, we now turn to a variety of its useful features.

   Control flow
       The shell contains a number of commands which can be used  to  regulate
       the  flow  of  control in command files (shell scripts) and (in limited
       but useful ways) from terminal input.  These commands  all  operate  by
       forcing  the  shell  to  reread  or  skip  in its input and, due to the
       implementation, restrict the placement of some of the commands.

       The foreach, switch, and while statements, as well as the  if-then-else
       form  of  the if statement, require that the major keywords appear in a
       single simple command on an input line as shown below.

       If the shell’s input is  not  seekable,  the  shell  buffers  up  input
       whenever  a  loop  is  being  read  and performs seeks in this internal
       buffer to accomplish the rereading implied by the loop.  (To the extent
       that  this allows, backward gotos will succeed on non-seekable inputs.)

   Expressions
       The if, while and exit builtin commands use expressions with  a  common
       syntax.   The expressions can include any of the operators described in
       the next three sections.  Note that the @ builtin  command  (q.v.)  has
       its own separate syntax.

   Logical, arithmetical and comparison operators
       These operators are similar to those of C and have the same precedence.
       They include

           ||  &&  |  ^  &  ==  !=  =~  !~  <=  >=
           <  > <<  >>  +  -  *  /  %  !  ~  (  )

       Here the precedence increases to the right, ‘==’ ‘!=’  ‘=~’  and  ‘!~’,
       ‘<=’  ‘>=’  ‘<’  and  ‘>’,  ‘<<’ and ‘>>’, ‘+’ and ‘-’, ‘*’ ‘/’ and ‘%’
       being, in groups, at the same level.   The  ‘==’  ‘!=’  ‘=~’  and  ‘!~’
       operators  compare  their  arguments  as strings; all others operate on
       numbers.  The operators ‘=~’ and ‘!~’ are like  ‘!=’  and  ‘==’  except
       that  the right hand side is a glob-pattern (see Filename substitution)
       against which the left hand operand is matched.  This reduces the  need
       for use of the switch builtin command in shell scripts when all that is
       really needed is pattern matching.

       Strings which begin with ‘0’ are considered  octal  numbers.   Null  or
       missing  arguments  are considered ‘0’.  The results of all expressions
       are strings, which represent decimal numbers.  It is important to  note
       that  no  two  components of an expression can appear in the same word;
       except  when  adjacent  to  components   of   expressions   which   are
       syntactically  significant to the parser (‘&’ ‘|’ ‘<’ ‘>’ ‘(’ ‘)’) they
       should be surrounded by spaces.

   Command exit status
       Commands can be executed in expressions and their exit status  returned
       by enclosing them in braces (‘{}’).  Remember that the braces should be
       separated from the words of the command by spaces.  Command  executions
       succeed, returning true, i.e., ‘1’, if the command exits with status 0,
       otherwise they fail, returning false,  i.e.,  ‘0’.   If  more  detailed
       status  information  is  required  then  the command should be executed
       outside of an expression and the status shell variable examined.

   File inquiry operators
       Some of these operators perform true/false tests on files  and  related
       objects.  They are of the form -op file, where op is one of

           r   Read access
           w   Write access
           x   Execute access
           X   Executable  in the path or shell builtin, e.g., ‘-X ls’ and ‘-X
               ls-F’ are generally true, but ‘-X /bin/ls’ is not (+)
           e   Existence
           o   Ownership
           z   Zero size
           s   Non-zero size (+)
           f   Plain file
           d   Directory
           l   Symbolic link (+) *
           b   Block special file (+)
           c   Character special file (+)
           p   Named pipe (fifo) (+) *
           S   Socket special file (+) *
           u   Set-user-ID bit is set (+)
           g   Set-group-ID bit is set (+)
           k   Sticky bit is set (+)
           t   file (which must be a digit) is an open file descriptor  for  a
               terminal device (+)
           R   Has been migrated (convex only) (+)
           L   Applies  subsequent  operators in a multiple-operator test to a
               symbolic link rather than to the file to which the link  points
               (+) *

       file  is command and filename expanded and then tested to see if it has
       the specified relationship to the real user.  If file does not exist or
       is  inaccessible  or,  for  the  operators  indicated  by  ‘*’,  if the
       specified file type does not exist on  the  current  system,  then  all
       enquiries return false, i.e., ‘0’.

       These  operators  may  be  combined  for  conciseness:  ‘-xy  file’  is
       equivalent to ‘-x file && -y file’.  (+) For  example,  ‘-fx’  is  true
       (returns ‘1’) for plain executable files, but not for directories.

       L may be used in a multiple-operator test to apply subsequent operators
       to a symbolic link rather than to the file to which  the  link  points.
       For  example, ‘-lLo’ is true for links owned by the invoking user.  Lr,
       Lw and Lx are always true for links and false for non-links.  L  has  a
       different  meaning  when it is the last operator in a multiple-operator
       test; see below.

       It is possible but not useful, and  sometimes  misleading,  to  combine
       operators  which  expect file to be a file with operators which do not,
       (e.g., X and t).  Following L with a  non-file  operator  can  lead  to
       particularly strange results.

       Other  operators  return  other information, i.e., not just ‘0’ or ‘1’.
       (+) They have the same format as before; op may be one of

           A       Last file access time, as the number of seconds  since  the
                   epoch
           A:      Like A, but in timestamp format, e.g., ‘Fri May 14 16:36:10
                   1993’
           M       Last file modification time
           M:      Like M, but in timestamp format
           C       Last inode modification time
           C:      Like C, but in timestamp format
           D       Device number
           I       Inode number
           F       Composite file identifier, in the form device:inode
           L       The name of the file pointed to by a symbolic link
           N       Number of (hard) links
           P       Permissions, in octal, without leading zero
           P:      Like P, with leading zero
           Pmode   Equivalent to ‘-P file & mode’, e.g., ‘-P22  file’  returns
                   ‘22’  if  file  is  writable by group and other, ‘20’ if by
                   group only, and ‘0’ if by neither
           Pmode:  Like Pmode:, with leading zero
           U       Numeric userid
           U:      Username, or the numeric userid if the username is unknown
           G       Numeric groupid
           G:      Groupname, or the  numeric  groupid  if  the  groupname  is
                   unknown
           Z       Size, in bytes

       Only one of these operators may appear in a multiple-operator test, and
       it must be the last.  Note that L has a different meaning at the end of
       and  elsewhere  in  a  multiple-operator  test.  Because ‘0’ is a valid
       return value for many of these operators, they do not return  ‘0’  when
       they fail: most return ‘-1’, and F returns ‘:’.

       If  the  shell  is  compiled  with POSIX defined (see the version shell
       variable), the result of a file inquiry is based on the permission bits
       of  the  file  and not on the result of the access(2) system call.  For
       example, if one tests a file with -w whose permissions would ordinarily
       allow writing but which is on a file system mounted read-only, the test
       will succeed in a POSIX shell but fail in a non-POSIX shell.

       File inquiry operators can also be evaluated with the filetest  builtin
       command (q.v.) (+).

   Jobs
       The  shell  associates  a  job with each pipeline.  It keeps a table of
       current jobs, printed by the  jobs  command,  and  assigns  them  small
       integer  numbers.   When  a job is started asynchronously with ‘&’, the
       shell prints a line which looks like

           [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process id was 1234.

       If  you are running a job and wish to do something else you may hit the
       suspend key (usually ‘^Z’), which sends a STOP signal  to  the  current
       job.   The  shell  will  then  normally  indicate that the job has been
       ‘Suspended’ and print another prompt.  If the listjobs  shell  variable
       is set, all jobs will be listed like the jobs builtin command; if it is
       set to ‘long’ the listing will be in long format, like ‘jobs -l’.   You
       can  then manipulate the state of the suspended job.  You can put it in
       the ‘‘background’’ with the bg command or run some other  commands  and
       eventually  bring  the  job back into the ‘‘foreground’’ with fg.  (See
       also  the  run-fg-editor  editor  command.)   A   ‘^Z’   takes   effect
       immediately  and is like an interrupt in that pending output and unread
       input are discarded when it is typed.  The wait builtin command  causes
       the shell to wait for all background jobs to complete.

       The  ‘^]’ key sends a delayed suspend signal, which does not generate a
       STOP signal until a program attempts to read(2) it, to the current job.
       This  can  usefully be typed ahead when you have prepared some commands
       for a job which you wish to stop after it has read them.  The ‘^Y’  key
       performs  this function in csh(1); in tcsh, ‘^Y’ is an editing command.
       (+)

       A job being run in the background stops if it tries to  read  from  the
       terminal.   Background jobs are normally allowed to produce output, but
       this can be disabled by giving the command ‘stty tostop’.  If  you  set
       this  tty  option,  then  background  jobs  will  stop when they try to
       produce output like they do when they try to read input.

       There are several ways to refer to jobs in the  shell.   The  character
       ‘%’  introduces  a job name.  If you wish to refer to job number 1, you
       can name it as ‘%1’.  Just naming a job brings it  to  the  foreground;
       thus  ‘%1’  is  a  synonym  for  ‘fg  %1’, bringing job 1 back into the
       foreground.  Similarly, saying ‘%1 &’ resumes job 1 in the  background,
       just like ‘bg %1’.  A job can also be named by an unambiguous prefix of
       the string typed in  to  start  it:  ‘%ex’  would  normally  restart  a
       suspended  ex(1)  job,  if there were only one suspended job whose name
       began with the string ‘ex’.  It is also possible to say  ‘%?string’  to
       specify  a  job  whose  text contains string, if there is only one such
       job.

       The shell maintains a notion of the  current  and  previous  jobs.   In
       output pertaining to jobs, the current job is marked with a ‘+’ and the
       previous job with a ‘-’.  The abbreviations ‘%+’, ‘%’, and (by  analogy
       with the syntax of the history mechanism) ‘%%’ all refer to the current
       job, and ‘%-’ refers to the previous job.

       The job control mechanism requires that the stty(1) option ‘new’ be set
       on  some systems.  It is an artifact from a ‘new’ implementation of the
       tty driver which allows generation of  interrupt  characters  from  the
       keyboard  to  tell  jobs  to  stop.   See stty(1) and the setty builtin
       command for details on setting options in the new tty driver.

   Status reporting
       The shell learns immediately whenever  a  process  changes  state.   It
       normally  informs you whenever a job becomes blocked so that no further
       progress is possible, but only right before it prints a  prompt.   This
       is  done so that it does not otherwise disturb your work.  If, however,
       you  set  the  shell  variable  notify,  the  shell  will  notify   you
       immediately  of  changes of status in background jobs.  There is also a
       shell command notify which marks a single process so  that  its  status
       changes  will  be  immediately  reported.   By default notify marks the
       current process; simply say ‘notify’ after starting a background job to
       mark it.

       When  you  try  to  leave the shell while jobs are stopped, you will be
       warned that ‘You have stopped jobs.’ You may use the  jobs  command  to
       see  what  they  are.  If you do this or immediately try to exit again,
       the shell will not warn you a second time, and the suspended jobs  will
       be terminated.

   Automatic, periodic and timed events (+)
       There  are  various  ways  to  run  commands  and  take  other  actions
       automatically at various times in the  ‘‘life  cycle’’  of  the  shell.
       They are summarized here, and described in detail under the appropriate
       Builtin commands, Special shell variables and Special aliases.

       The sched builtin command puts commands in a scheduled-event  list,  to
       be executed by the shell at a given time.

       The  beepcmd,  cwdcmd,  periodic,  precmd,  postcmd, and jobcmd Special
       aliases can be set, respectively, to execute commands  when  the  shell
       wants  to  ring  the  bell,  when  the working directory changes, every
       tperiod minutes, before each prompt, before each command gets executed,
       after  each  command  gets  executed,  and  when a job is started or is
       brought into the foreground.

       The autologout shell variable can be set to log out or lock  the  shell
       after a given number of minutes of inactivity.

       The  mail shell variable can be set to check for new mail periodically.

       The printexitvalue shell variable can be set to print the  exit  status
       of commands which exit with a status other than zero.

       The  rmstar  shell  variable can be set to ask the user, when ‘rm *’ is
       typed, if that is really what was meant.

       The time shell variable can be set to execute the time builtin  command
       after the completion of any process that takes more than a given number
       of CPU seconds.

       The watch and who shell variables can be set to  report  when  selected
       users log in or out, and the log builtin command reports on those users
       at any time.

   Native Language System support (+)
       The shell is eight bit clean (if so compiled;  see  the  version  shell
       variable)  and  thus  supports  character sets needing this capability.
       NLS support differs depending on whether or not the shell was  compiled
       to  use  the  system’s NLS (again, see version).  In either case, 7-bit
       ASCII is the default character code (e.g., the classification of  which
       characters  are  printable)  and  sorting,  and  changing  the  LANG or
       LC_CTYPE environment variables causes a check for possible  changes  in
       these respects.

       When  using  the  system’s  NLS, the setlocale(3) function is called to
       determine appropriate character code/classification and sorting  (e.g.,
       a  ’en_CA.UTF-8’  would  yield  "UTF-8"  as  a  character  code).  This
       function  typically  examines  the  LANG   and   LC_CTYPE   environment
       variables; refer to the system documentation for further details.  When
       not using the system’s NLS, the shell simulates it by assuming that the
       ISO  8859-1  character  set  is  used  whenever  either of the LANG and
       LC_CTYPE variables are set, regardless of their values.  Sorting is not
       affected for the simulated NLS.

       In addition, with both real and simulated NLS, all printable characters
       in the range \200-\377, i.e., those  that  have  M-char  bindings,  are
       automatically   rebound   to  self-insert-command.   The  corresponding
       binding for the escape-char sequence, if any,  is  left  alone.   These
       characters are not rebound if the NOREBIND environment variable is set.
       This may be useful for the simulated NLS or a primitive real NLS  which
       assumes  full  ISO 8859-1.  Otherwise, all M-char bindings in the range
       \240-\377 are effectively undone.  Explicitly  rebinding  the  relevant
       keys with bindkey is of course still possible.

       Unknown  characters (i.e., those that are neither printable nor control
       characters) are printed in the format \nnn.  If the tty is not in 8 bit
       mode,  other  8  bit characters are printed by converting them to ASCII
       and using standout mode.  The shell never changes the 7/8 bit  mode  of
       the  tty  and tracks user-initiated changes of 7/8 bit mode.  NLS users
       (or, for that matter, those who want to use a meta  key)  may  need  to
       explicitly  set  the  tty in 8 bit mode through the appropriate stty(1)
       command in, e.g., the ~/.login file.

   OS variant support (+)
       A number of new builtin commands are provided to  support  features  in
       particular  operating  systems.   All  are  described  in detail in the
       Builtin commands section.

       On  systems  that  support  TCF  (aix-ibm370,  aix-ps2),  getspath  and
       setspath  get  and set the system execution path, getxvers and setxvers
       get and set  the  experimental  version  prefix  and  migrate  migrates
       processes  between  sites.   The  jobs builtin prints the site on which
       each job is executing.

       Under BS2000, bs2cmd executes commands  of  the  underlying  BS2000/OSD
       operating system.

       Under   Domain/OS,   inlib   adds   shared  libraries  to  the  current
       environment, rootnode changes the rootnode and ver changes the systype.

       Under Mach, setpath is equivalent to Mach’s setpath(1).

       Under Masscomp/RTU and Harris CX/UX, universe sets the universe.

       Under  Harris  CX/UX,  ucb  or  att  runs a command under the specified
       universe.

       Under Convex/OS, warp prints or sets the universe.

       The  VENDOR,  OSTYPE  and  MACHTYPE  environment   variables   indicate
       respectively   the   vendor,   operating   system   and   machine  type
       (microprocessor class or machine model) of  the  system  on  which  the
       shell thinks it is running.  These are particularly useful when sharing
       one’s home directory between several types of machines;  one  can,  for
       example,

           set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .)

       in  one’s ~/.login and put executables compiled for each machine in the
       appropriate directory.

       The version shell variable indicates what options were chosen when  the
       shell was compiled.

       Note  also  the  newgrp  builtin,  the  afsuser  and  echo_style  shell
       variables and the system-dependent locations of the shell’s input files
       (see FILES).

   Signal handling
       Login  shells  ignore  interrupts when reading the file ~/.logout.  The
       shell ignores quit signals unless started with -q.  Login shells  catch
       the  terminate  signal,  but  non-login  shells  inherit  the terminate
       behavior from their parents.  Other signals have the values  which  the
       shell inherited from its parent.

       In  shell  scripts,  the  shell’s  handling  of interrupt and terminate
       signals can be controlled with onintr, and its handling of hangups  can
       be controlled with hup and nohup.

       The  shell  exits on a hangup (see also the logout shell variable).  By
       default, the shell’s children do too, but the shell does not send  them
       a hangup when it exits.  hup arranges for the shell to send a hangup to
       a child when it exits, and nohup sets a child to ignore hangups.

   Terminal management (+)
       The shell uses  three  different  sets  of  terminal  (‘‘tty’’)  modes:
       ‘edit’,   used   when  editing,  ‘quote’,  used  when  quoting  literal
       characters, and ‘execute’, used when  executing  commands.   The  shell
       holds  some settings in each mode constant, so commands which leave the
       tty in a confused state do not interfere with  the  shell.   The  shell
       also  matches changes in the speed and padding of the tty.  The list of
       tty modes that are kept constant can be examined and modified with  the
       setty  builtin.  Note that although the editor uses CBREAK mode (or its
       equivalent), it takes typed-ahead characters anyway.

       The echotc, settc and telltc commands can be  used  to  manipulate  and
       debug terminal capabilities from the command line.

       On  systems  that  support  SIGWINCH  or SIGWINDOW, the shell adapts to
       window resizing automatically and  adjusts  the  environment  variables
       LINES and COLUMNS if set.  If the environment variable TERMCAP contains
       li# and co# fields, the shell adjusts them to reflect  the  new  window
       size.

REFERENCE

       The  next sections of this manual describe all of the available Builtin
       commands, Special aliases and Special shell variables.

   Builtin commands
       %job    A synonym for the fg builtin command.

       %job &  A synonym for the bg builtin command.

       :       Does nothing, successfully.

       @
       @ name = expr
       @ name[index] = expr
       @ name++|--
       @ name[index]++|--
               The first form prints the values of all shell variables.

               The second form assigns the value of expr to name.   The  third
               form  assigns  the  value  of expr to the index’th component of
               name; both name and its index’th component must already  exist.

               expr  may  contain  the  operators ‘*’, ‘+’, etc., as in C.  If
               expr contains ‘<’, ‘>’, ‘&’ or ‘’ then at least  that  part  of
               expr  must be placed within ‘()’.  Note that the syntax of expr
               has nothing to do with that described under Expressions.

               The fourth and fifth forms increment (‘++’) or decrement (‘--’)
               name or its index’th component.

               The space between ‘@’ and name is required.  The spaces between
               name and ‘=’ and between ‘=’ and expr are optional.  Components
               of expr must be separated by spaces.

       alias [name [wordlist]]
               Without  arguments,  prints all aliases.  With name, prints the
               alias for name.  With name and wordlist,  assigns  wordlist  as
               the   alias   of   name.   wordlist  is  command  and  filename
               substituted.  name may not be ‘alias’ or ‘unalias’.   See  also
               the unalias builtin command.

       alloc   Shows  the  amount of dynamic memory acquired, broken down into
               used and free memory.  With an argument  shows  the  number  of
               free  and  used  blocks  in each size category.  The categories
               start at size 8 and double at each step.  This command’s output
               may  vary  across  system types, because systems other than the
               VAX may use a different memory allocator.

       bg [%job ...]
               Puts the specified jobs (or,  without  arguments,  the  current
               job)  into  the  background,  continuing each if it is stopped.
               job may be a number, a string, ‘’, ‘%’, ‘+’ or ‘-’ as described
               under Jobs.

       bindkey [-l|-d|-e|-v|-u] (+)
       bindkey [-a] [-b] [-k] [-r] [--] key (+)
       bindkey [-a] [-b] [-k] [-c|-s] [--] key command (+)
               Without  options,  the  first form lists all bound keys and the
               editor command to which each is bound, the  second  form  lists
               the  editor  command  to  which key is bound and the third form
               binds the editor command command to key.  Options include:

               -l  Lists all editor commands and a short description of  each.
               -d  Binds  all  keys  to  the standard bindings for the default
                   editor.
               -e  Binds all keys to the standard GNU Emacs-like bindings.
               -v  Binds all keys to the standard vi(1)-like bindings.
               -a  Lists or changes key-bindings in the alternative  key  map.
                   This is the key map used in vi command mode.
               -b  key   is   interpreted   as  a  control  character  written
                   ^character (e.g., ‘^A’) or  C-character  (e.g.,  ‘C-A’),  a
                   meta   character   written  M-character  (e.g.,  ‘M-A’),  a
                   function key written F-string  (e.g.,  ‘F-string’),  or  an
                   extended prefix key written X-character (e.g., ‘X-A’).
               -k  key  is interpreted as a symbolic arrow key name, which may
                   be one of ‘down’, ‘up’, ‘left’ or ‘right’.
               -r  Removes key’s binding.  Be careful: ‘bindkey -r’  does  not
                   bind  key  to  self-insert-command  (q.v.),  it unbinds key
                   completely.
               -c  command is interpreted as a  builtin  or  external  command
                   instead of an editor command.
               -s  command  is  taken  as  a  literal  string  and  treated as
                   terminal input when key is typed.  Bound  keys  in  command
                   are  themselves  reinterpreted,  and this continues for ten
                   levels of interpretation.
               --  Forces a break from option processing, so the next word  is
                   taken as key even if it begins with ’-’.
               -u (or any invalid option)
                   Prints a usage message.

               key  may  be  a  single character or a string.  If a command is
               bound to a string, the first character of the string  is  bound
               to  sequence-lead-in  and  the  entire  string  is bound to the
               command.

               Control characters in key can be literal (they can be typed  by
               preceding  them with the editor command quoted-insert, normally
               bound to ‘^V’) or written caret-character  style,  e.g.,  ‘^A’.
               Delete is written ‘^?’  (caret-question mark).  key and command
               can contain backslashed  escape  sequences  (in  the  style  of
               System V echo(1)) as follows:

                   \a      Bell
                   \b      Backspace
                   \e      Escape
                   \f      Form feed
                   \n      Newline
                   \r      Carriage return
                   \t      Horizontal tab
                   \v      Vertical tab
                   \nnn    The  ASCII  character  corresponding  to  the octal
                           number nnn

               ‘\’ nullifies the special meaning of the  following  character,
               if it has any, notably ‘\’ and ‘^’.

       bs2cmd bs2000-command (+)
               Passes  bs2000-command  to  the  BS2000 command interpreter for
               execution. Only non-interactive commands can be  executed,  and
               it  is  not  possible to execute any command that would overlay
               the image of the  current  process,  like  /EXECUTE  or  /CALL-
               PROCEDURE. (BS2000 only)

       break   Causes  execution  to  resume  after  the  end  of  the nearest
               enclosing foreach or while.   The  remaining  commands  on  the
               current   line  are  executed.   Multi-level  breaks  are  thus
               possible by writing them all on one line.

       breaksw Causes a break from a switch, resuming after the endsw.

       builtins (+)
               Prints the names of all builtin commands.

       bye (+) A synonym for the logout builtin command.   Available  only  if
               the shell was so compiled; see the version shell variable.

       case label:
               A label in a switch statement as discussed below.

       cd [-p] [-l] [-n|-v] [name]
               If  a  directory  name  is  given,  changes the shell’s working
               directory to name.  If not, changes to home.  If name is ‘-’ it
               is  interpreted  as  the  previous working directory (see Other
               substitutions).  (+) If name  is  not  a  subdirectory  of  the
               current directory (and does not begin with ‘/’, ‘./’ or ‘../’),
               each component of the variable cdpath is checked to see  if  it
               has  a  subdirectory name.  Finally, if all else fails but name
               is a shell variable whose value begins with ‘/’, then  this  is
               tried to see if it is a directory.

               With -p, prints the final directory stack, just like dirs.  The
               -l, -n and -v flags have the same effect on cd as on dirs,  and
               they imply -p.  (+)

               See also the implicitcd shell variable.

       chdir   A synonym for the cd builtin command.

       complete [command [word/pattern/list[:select]/[[suffix]/] ...]] (+)
               Without  arguments, lists all completions.  With command, lists
               completions for command.  With command and word  etc.,  defines
               completions.

               command  may  be  a  full  command  name or a glob-pattern (see
               Filename substitution).  It can begin with ‘-’ to indicate that
               completion should be used only when command is ambiguous.

               word specifies which word relative to the current word is to be
               completed, and may be one of the following:

                   c   Current-word completion.   pattern  is  a  glob-pattern
                       which  must  match the beginning of the current word on
                       the command line.  pattern is ignored  when  completing
                       the current word.
                   C   Like  c,  but  includes  pattern  when  completing  the
                       current word.
                   n   Next-word completion.  pattern is a glob-pattern  which
                       must  match  the  beginning of the previous word on the
                       command line.
                   N   Like n, but must match the beginning of  the  word  two
                       before the current word.
                   p   Position-dependent  completion.   pattern  is a numeric
                       range,  with  the  same  syntax  used  to  index  shell
                       variables, which must include the current word.

               list,  the  list  of  possible  completions,  may be one of the
               following:

                   a       Aliases
                   b       Bindings (editor commands)
                   c       Commands (builtin or external commands)
                   C       External commands which  begin  with  the  supplied
                           path prefix
                   d       Directories
                   D       Directories  which  begin  with  the  supplied path
                           prefix
                   e       Environment variables
                   f       Filenames
                   F       Filenames which begin with the supplied path prefix
                   g       Groupnames
                   j       Jobs
                   l       Limits
                   n       Nothing
                   s       Shell variables
                   S       Signals
                   t       Plain (‘‘text’’) files
                   T       Plain   (‘‘text’’)   files  which  begin  with  the
                           supplied path prefix
                   v       Any variables
                   u       Usernames
                   x       Like n, but  prints  select  when  list-choices  is
                           used.
                   X       Completions
                   $var    Words from the variable var
                   (...)   Words from the given list
                   ‘...‘   Words from the output of command

               select  is an optional glob-pattern.  If given, words from only
               list that match select are considered  and  the  fignore  shell
               variable  is  ignored.   The last three types of completion may
               not have a select pattern, and x uses select as an  explanatory
               message when the list-choices editor command is used.

               suffix  is  a  single  character to be appended to a successful
               completion.  If null, no character is appended.  If omitted (in
               which  case  the fourth delimiter can also be omitted), a slash
               is appended to directories and a space to other words.

               Now for some examples.  Some commands take only directories  as
               arguments, so there’s no point completing plain files.

                   > complete cd ’p/1/d/’

               completes  only  the  first  word following ‘cd’ (‘p/1’) with a
               directory.  p-type completion can also be used to  narrow  down
               command completion:

                   > co[^D]
                   complete compress
                   > complete -co* ’p/0/(compress)/’
                   > co[^D]
                   > compress

               This completion completes commands (words in position 0, ‘p/0’)
               which begin with ‘co’ (thus matching ‘co*’) to ‘compress’  (the
               only  word  in  the list).  The leading ‘-’ indicates that this
               completion is to be used with only ambiguous commands.

                   > complete find ’n/-user/u/’

               is an example of n-type completion.  Any word following  ‘find’
               and immediately following ‘-user’ is completed from the list of
               users.

                   > complete cc ’c/-I/d/’

               demonstrates c-type completion.  Any word  following  ‘cc’  and
               beginning  with  ‘-I’ is completed as a directory.  ‘-I’ is not
               taken as part of the directory because we used lowercase c.

               Different lists are useful with different commands.

                   > complete alias ’p/1/a/’
                   > complete man ’p/*/c/’
                   > complete set ’p/1/s/’
                   > complete true ’p/1/x:Truth has no options./’

               These complete words following ‘alias’ with aliases, ‘man’ with
               commands,  and ‘set’ with shell variables.  ‘true’ doesn’t have
               any options, so x does nothing when completion is attempted and
               prints  ‘Truth  has  no  options.’  when completion choices are
               listed.

               Note that the man example, and several  other  examples  below,
               could just as well have used ’c/*’ or ’n/*’ as ’p/*’.

               Words  can be completed from a variable evaluated at completion
               time,

                   > complete ftp ’p/1/$hostnames/’
                   > set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu)
                   > ftp [^D]
                   rtfm.mit.edu tesla.ee.cornell.edu
                   > ftp [^C]
                   >  set  hostnames  =   (rtfm.mit.edu   tesla.ee.cornell.edu
                   uunet.uu.net)
                   > ftp [^D]
                   rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net

               or from a command run at completion time:

                   > complete kill ’p/*/‘ps | awk \{print\ \$1\}‘/’
                   > kill -9 [^D]
                   23113 23377 23380 23406 23429 23529 23530 PID

               Note  that  the  complete  command  does  not  itself quote its
               arguments, so the braces, space and ‘$’ in ‘{print $1}’ must be
               quoted explicitly.

               One command can have multiple completions:

                   > complete dbx ’p/2/(core)/’ ’p/*/c/’

               completes the second argument to ‘dbx’ with the word ‘core’ and
               all other arguments with commands.  Note  that  the  positional
               completion   is  specified  before  the  next-word  completion.
               Because completions are evaluated from left to  right,  if  the
               next-word completion were specified first it would always match
               and the positional completion would never be executed.  This is
               a common mistake when defining a completion.

               The  select  pattern  is useful when a command takes files with
               only particular forms as arguments.  For example,

                   > complete cc ’p/*/f:*.[cao]/’

               completes ‘cc’ arguments to files ending in only ‘.c’, ‘.a’, or
               ‘.o’.  select can also exclude files, using negation of a glob-
               pattern as described under Filename  substitution.   One  might
               use

                   > complete rm ’p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/’

               to  exclude  precious  source  code  from  ‘rm’ completion.  Of
               course,  one  could  still  type  excluded  names  manually  or
               override  the  completion mechanism using the complete-word-raw
               or list-choices-raw editor commands (q.v.).

               The ‘C’, ‘D’, ‘F’ and ‘T’ lists are like ‘c’, ‘d’, ‘f’ and  ‘t’
               respectively,  but  they use the select argument in a different
               way:  to  restrict  completion  to  files  beginning   with   a
               particular path prefix.  For example, the Elm mail program uses
               ‘=’ as an abbreviation for one’s mail directory.  One might use

                   > complete elm c@=@F:$HOME/Mail/@

               to  complete  ‘elm  -f =’ as if it were ‘elm -f ~/Mail/’.  Note
               that we used ‘@’ instead of ‘/’ to  avoid  confusion  with  the
               select  argument,  and  we  used ‘$HOME’ instead of ‘~’ because
               home directory substitution works at only the  beginning  of  a
               word.

               suffix  is  used  to add a nonstandard suffix (not space or ‘/’
               for directories) to completed words.

                   > complete finger ’c/*@/$hostnames/’ ’p/1/u/@’

               completes arguments to ‘finger’ from the list of users, appends
               an  ‘@’,  and then completes after the ‘@’ from the ‘hostnames’
               variable.  Note again the order in which  the  completions  are
               specified.

               Finally, here’s a complex example for inspiration:

                   > complete find \
                   ’n/-name/f/’ ’n/-newer/f/’ ’n/-{,n}cpio/f/’ \
                   ’n/-exec/c/’ ’n/-ok/c/’ ’n/-user/u/’ \
                   ’n/-group/g/’ ’n/-fstype/(nfs 4.2)/’ \
                   ’n/-type/(b c d f l p s)/’ \
                   ’c/-/(name newer cpio ncpio exec ok user \
                   group fstype type atime ctime depth inum \
                   ls mtime nogroup nouser perm print prune \
                   size xdev)/’ \
                   ’p/*/d/’

               This  completes  words  following ‘-name’, ‘-newer’, ‘-cpio’ or
               ‘ncpio’ (note the pattern which matches both) to  files,  words
               following  ‘-exec’ or ‘-ok’ to commands, words following ‘user’
               and  ‘group’  to  users  and  groups  respectively  and   words
               following  ‘-fstype’  or ‘-type’ to members of the given lists.
               It also completes the switches themselves from the  given  list
               (note  the use of c-type completion) and completes anything not
               otherwise completed to a directory.  Whew.

               Remember that programmed completions are ignored  if  the  word
               being completed is a tilde substitution (beginning with ‘~’) or
               a variable (beginning with ‘$’).  complete is  an  experimental
               feature,  and  the  syntax may change in future versions of the
               shell.  See also the uncomplete builtin command.

       continue
               Continues execution of the nearest enclosing while or  foreach.
               The rest of the commands on the current line are executed.

       default:
               Labels  the default case in a switch statement.  It should come
               after all case labels.

       dirs [-l] [-n|-v]
       dirs -S|-L [filename] (+)
       dirs -c (+)
               The first form prints the directory  stack.   The  top  of  the
               stack  is  at  the left and the first directory in the stack is
               the current directory.  With -l, ‘~’ or ‘~name’ in  the  output
               is  expanded  explicitly  to  home  or the pathname of the home
               directory for user name.  (+)  With  -n,  entries  are  wrapped
               before they reach the edge of the screen.  (+) With -v, entries
               are printed one per line, preceded by  their  stack  positions.
               (+) If more than one of -n or -v is given, -v takes precedence.
               -p is accepted but does nothing.

               With -S, the second form saves the directory stack to  filename
               as  a  series  of  cd  and  pushd commands.  With -L, the shell
               sources filename, which is presumably a  directory  stack  file
               saved  by  the  -S option or the savedirs mechanism.  In either
               case, dirsfile is used if filename is not given and  ~/.cshdirs
               is used if dirsfile is unset.

               Note  that  login  shells  do  the  equivalent  of ‘dirs -L’ on
               startup and, if savedirs is  set,  ‘dirs  -S’  before  exiting.
               Because  only  ~/.tcshrc is normally sourced before ~/.cshdirs,
               dirsfile should be set in ~/.tcshrc rather than ~/.login.

               The last form clears the directory stack.

       echo [-n] word ...
               Writes each word to the shell’s standard output,  separated  by
               spaces  and  terminated  with  a newline.  The echo_style shell
               variable may be set to emulate (or not) the  flags  and  escape
               sequences  of  the  BSD  and/or  System V versions of echo; see
               echo(1).

       echotc [-sv] arg ... (+)
               Exercises the terminal capabilities (see termcap(5))  in  args.
               For  example,  ’echotc  home’  sends  the  cursor  to  the home
               position, ’echotc cm 3 10’ sends it to column 3 and row 10, and
               ’echotc  ts  0; echo "This is a test."; echotc fs’ prints "This
               is a test."  in the status line.

               If arg is ’baud’, ’cols’, ’lines’, ’meta’ or ’tabs’, prints the
               value  of  that  capability  ("yes" or "no" indicating that the
               terminal does or does not have that capability).  One might use
               this  to  make  the  output from a shell script less verbose on
               slow terminals, or limit command output to the number of  lines
               on the screen:

                   > set history=‘echotc lines‘

                   > @ history--
               Termcap  strings  may  contain  wildcards  which  will not echo
               correctly.  One should use double quotes when setting  a  shell
               variable  to  a terminal capability string, as in the following
               example that places the date in the status line:

                   > set tosl="‘echotc ts 0‘"
                   > set frsl="‘echotc fs‘"
                   > echo -n "$tosl";date; echo -n "$frsl"

               With -s,  nonexistent  capabilities  return  the  empty  string
               rather than causing an error.  With -v, messages are verbose.

       else
       end
       endif
       endsw   See  the  description  of  the  foreach,  if, switch, and while
               statements below.

       eval arg ...
               Treats the arguments as input to the  shell  and  executes  the
               resulting command(s) in the context of the current shell.  This
               is usually used to execute commands generated as the result  of
               command or variable substitution, because parsing occurs before
               these substitutions.  See tset(1) for a sample use of eval.

       exec command
               Executes the specified command in place of the current shell.

       exit [expr]
               The shell exits either with the value of the specified expr (an
               expression,  as  described under Expressions) or, without expr,
               with the value of the status variable.

       fg [%job ...]
               Brings the specified jobs (or, without arguments,  the  current
               job)  into  the  foreground,  continuing each if it is stopped.
               job may be a number, a string, ‘’, ‘%’, ‘+’ or ‘-’ as described
               under Jobs.  See also the run-fg-editor editor command.

       filetest -op file ... (+)
               Applies op (which is a file inquiry operator as described under
               File inquiry operators) to each file and returns the results as
               a space-separated list.

       foreach name (wordlist)
       ...
       end     Successively  sets the variable name to each member of wordlist
               and executes the sequence of commands between this command  and
               the  matching  end.  (Both foreach and end must appear alone on
               separate lines.)  The builtin command continue may be  used  to
               continue  the loop prematurely and the builtin command break to
               terminate it prematurely.  When this command is read  from  the
               terminal,  the loop is read once prompting with ‘foreach? ’ (or
               prompt2) before any statements in the loop  are  executed.   If
               you make a mistake typing in a loop at the terminal you can rub
               it out.

       getspath (+)
               Prints the system execution path.  (TCF only)

       getxvers (+)
               Prints the experimental version prefix.  (TCF only)

       glob wordlist
               Like echo, but no ‘\’ escapes  are  recognized  and  words  are
               delimited  by  null  characters  in  the  output.   Useful  for
               programs which wish to use the shell to filename expand a  list
               of words.

       goto word
               word  is  filename and command-substituted to yield a string of
               the form ‘label’.  The shell  rewinds  its  input  as  much  as
               possible,  searches  for  a line of the form ‘label:’, possibly
               preceded by blanks or tabs, and continues execution after  that
               line.

       hashstat
               Prints  a statistics line indicating how effective the internal
               hash table has been at locating commands (and avoiding exec’s).
               An  exec  is attempted for each component of the path where the
               hash function indicates a possible hit, and in  each  component
               which does not begin with a ‘/’.

               On  machines  without vfork(2), prints only the number and size
               of hash buckets.

       history [-hTr] [n]
       history -S|-L|-M [filename] (+)
       history -c (+)
               The first form prints the history event list.  If  n  is  given
               only  the  n most recent events are printed or saved.  With -h,
               the history list is printed without leading numbers.  If -T  is
               specified,  timestamps are printed also in comment form.  (This
               can be used to produce files suitable for loading with ’history
               -L’  or  ’source  -h’.)  With -r, the order of printing is most
               recent first rather than oldest first.

               With -S, the second form saves the history  list  to  filename.
               If  the  first  word of the savehist shell variable is set to a
               number, at most that many lines are saved.  If the second  word
               of  savehist is set to ‘merge’, the history list is merged with
               the existing history file instead of replacing it (if there  is
               one)  and sorted by time stamp.  (+) Merging is intended for an
               environment like the X Window System  with  several  shells  in
               simultaneous  use.   Currently it succeeds only when the shells
               quit nicely one after another.

               With -L, the shell appends  filename,  which  is  presumably  a
               history  list saved by the -S option or the savehist mechanism,
               to the history list.  -M  is  like  -L,  but  the  contents  of
               filename  are  merged  into  the  history  list  and  sorted by
               timestamp.  In either case, histfile is used if filename is not
               given  and  ~/.history  is used if histfile is unset.  ‘history
               -L’ is exactly like ’source -h’ except that it does not require
               a filename.

               Note  that  login  shells  do the equivalent of ‘history -L’ on
               startup and, if savehist is set, ‘history -S’  before  exiting.
               Because  only  ~/.tcshrc is normally sourced before ~/.history,
               histfile should be set in ~/.tcshrc rather than ~/.login.

               If histlit is set, the first and second forms  print  and  save
               the literal (unexpanded) form of the history list.

               The last form clears the history list.

       hup [command] (+)
               With  command,  runs command such that it will exit on a hangup
               signal and arranges for the shell to send it  a  hangup  signal
               when  the  shell  exits.   Note that commands may set their own
               response to  hangups,  overriding  hup.   Without  an  argument
               (allowed in only a shell script), causes the shell to exit on a
               hangup for the  remainder  of  the  script.   See  also  Signal
               handling and the nohup builtin command.

       if (expr) command
               If   expr  (an  expression,  as  described  under  Expressions)
               evaluates   true,   then   command   is   executed.    Variable
               substitution on command happens early, at the same time it does
               for the rest of the if  command.   command  must  be  a  simple
               command,  not  an  alias,  a  pipeline,  a  command  list  or a
               parenthesized  command  list,  but  it  may   have   arguments.
               Input/output  redirection  occurs  even  if  expr  is false and
               command is thus not executed; this is a bug.

       if (expr) then
       ...
       else if (expr2) then
       ...
       else
       ...
       endif   If the specified expr is true then the commands  to  the  first
               else are executed; otherwise if expr2 is true then the commands
               to the second else are executed, etc.  Any  number  of  else-if
               pairs are possible; only one endif is needed.  The else part is
               likewise optional.  (The words else and endif  must  appear  at
               the  beginning  of input lines; the if must appear alone on its
               input line or after an else.)

       inlib shared-library ... (+)
               Adds each shared-library to the current environment.  There  is
               no way to remove a shared library.  (Domain/OS only)

       jobs [-l]
               Lists  the active jobs.  With -l, lists process IDs in addition
               to the normal information.  On TCF systems, prints the site  on
               which each job is executing.

       kill [-s signal] %job|pid ...
       kill -l The  first  and second forms sends the specified signal (or, if
               none is given, the TERM (terminate) signal)  to  the  specified
               jobs or processes.  job may be a number, a string, ‘’, ‘%’, ‘+’
               or ‘-’ as described under Jobs.  Signals are  either  given  by
               number  or by name (as given in /usr/include/signal.h, stripped
               of the prefix ‘SIG’).  There is no  default  job;  saying  just
               ‘kill’  does  not  send  a  signal  to the current job.  If the
               signal being sent is TERM (terminate) or HUP (hangup), then the
               job  or  process is sent a CONT (continue) signal as well.  The
               third form lists the signal names.

       limit [-h] [resource [maximum-use]]
               Limits the consumption by the current process and each  process
               it  creates  to  not  individually  exceed  maximum-use  on the
               specified resource.  If  no  maximum-use  is  given,  then  the
               current  limit  is  printed;  if no resource is given, then all
               limitations are given.  If the  -h  flag  is  given,  the  hard
               limits are used instead of the current limits.  The hard limits
               impose a ceiling on the values of the current limits.  Only the
               super-user  may  raise the hard limits, but a user may lower or
               raise the current limits within the legal range.

               Controllable resources currently include (if supported  by  the
               OS):

               cputime
                      the  maximum  number  of  cpu-seconds to be used by each
                      process

               filesize
                      the largest single file which can be created

               datasize
                      the maximum growth of the data+stack region via  sbrk(2)
                      beyond the end of the program text

               stacksize
                      the  maximum  size  of  the automatically-extended stack
                      region

               coredumpsize
                      the size of the largest core dump that will be created

               memoryuse
                      the maximum amount of physical memory a process may have
                      allocated to it at a given time

               heapsize
                      the  maximum amount of memory a process may allocate per
                      brk() system call

               descriptors or openfiles
                      the maximum number of open files for this process

               concurrency
                      the maximum number of threads for this process

               memorylocked
                      the maximum size which a process may  lock  into  memory
                      using mlock(2)

               maxproc
                      the  maximum  number  of simultaneous processes for this
                      user id

               sbsize the maximum size of socket buffer usage for this user

               maximum-use may be given  as  a  (floating  point  or  integer)
               number  followed  by a scale factor.  For all limits other than
               cputime the default scale is ‘k’ or ‘kilobytes’ (1024 bytes); a
               scale  factor  of  ‘m’  or  ‘megabytes’  may also be used.  For
               cputime the default scaling is ‘seconds’, while ‘m’ for minutes
               or  ‘h’ for hours, or a time of the form ‘mm:ss’ giving minutes
               and seconds may be used.

               For both resource names and scale factors, unambiguous prefixes
               of the names suffice.

       log (+) Prints  the  watch  shell  variable  and  reports  on each user
               indicated in watch who is logged in, regardless  of  when  they
               last logged in.  See also watchlog.

       login   Terminates  a  login  shell,  replacing  it with an instance of
               /bin/login.  This  is  one  way  to  log  off,   included   for
               compatibility with sh(1).

       logout  Terminates  a  login  shell.  Especially useful if ignoreeof is
               set.

       ls-F [-switch ...] [file ...] (+)
               Lists files like ‘ls -F’, but much faster.  It identifies  each
               type of special file in the listing with a special character:

               /   Directory
               *   Executable
               #   Block device
               %   Character device
               |   Named pipe (systems with named pipes only)
               =   Socket (systems with sockets only)
               @   Symbolic link (systems with symbolic links only)
               +   Hidden  directory  (AIX  only)  or context dependent (HP/UX
                   only)
               :   Network special (HP/UX only)

               If the listlinks shell variable  is  set,  symbolic  links  are
               identified  in  more detail (on only systems that have them, of
               course):

               @   Symbolic link to a non-directory
               >   Symbolic link to a directory
               &   Symbolic link to nowhere

               listlinks also slows down ls-F and  causes  partitions  holding
               files pointed to by symbolic links to be mounted.

               If  the  listflags shell variable is set to ‘x’, ‘a’ or ‘A’, or
               any combination thereof (e.g., ‘xA’), they are used as flags to
               ls-F,  making  it  act  like  ‘ls -xF’, ‘ls -Fa’, ‘ls -FA’ or a
               combination (e.g., ‘ls -FxA’).  On machines where  ‘ls  -C’  is
               not  the  default,  ls-F  acts  like ‘ls -CF’, unless listflags
               contains an ‘x’, in which case it acts  like  ‘ls  -xF’.   ls-F
               passes  its  arguments to ls(1) if it is given any switches, so
               ‘alias ls ls-F’ generally does the right thing.

               The  ls-F  builtin  can  list  files  using  different   colors
               depending  on  the  filetype  or extension.  See the color tcsh
               variable and the LS_COLORS environment variable.

       migrate [-site] pid|%jobid ... (+)
       migrate -site (+)
               The first  form  migrates  the  process  or  job  to  the  site
               specified  or  the  default site determined by the system path.
               The second  form  is  equivalent  to  ‘migrate  -site  $$’:  it
               migrates  the current process to the specified site.  Migrating
               the shell itself can cause  unexpected  behavior,  because  the
               shell does not like to lose its tty.  (TCF only)

       newgrp [-] group (+)
               Equivalent  to ‘exec newgrp’; see newgrp(1).  Available only if
               the shell was so compiled; see the version shell variable.

       nice [+number] [command]
               Sets the scheduling priority  for  the  shell  to  number,  or,
               without  number,  to  4.   With  command,  runs  command at the
               appropriate priority.  The greater the number, the less cpu the
               process  gets.  The super-user may specify negative priority by
               using ‘nice -number ...’.  Command is always executed in a sub-
               shell,  and  the  restrictions  placed on commands in simple if
               statements apply.

       nohup [command]
               With command, runs command such  that  it  will  ignore  hangup
               signals.   Note  that  commands  may  set their own response to
               hangups, overriding nohup.  Without  an  argument  (allowed  in
               only  a  shell  script), causes the shell to ignore hangups for
               the remainder of the script.  See also Signal handling and  the
               hup builtin command.

       notify [%job ...]
               Causes  the  shell  to  notify the user asynchronously when the
               status of any of the specified  jobs  (or,  without  %job,  the
               current  job) changes, instead of waiting until the next prompt
               as is usual.  job may be a number, a string, ‘’,  ‘%’,  ‘+’  or
               ‘-’  as  described  under  Jobs.   See  also  the  notify shell
               variable.

       onintr [-|label]
               Controls the  action  of  the  shell  on  interrupts.   Without
               arguments,   restores  the  default  action  of  the  shell  on
               interrupts, which is to terminate shell scripts or to return to
               the  terminal  command  input  level.   With  ‘-’,  causes  all
               interrupts to be ignored.  With  label,  causes  the  shell  to
               execute a ‘goto label’ when an interrupt is received or a child
               process terminates because it was interrupted.

               onintr is ignored if the  shell  is  running  detached  and  in
               system startup files (see FILES), where interrupts are disabled
               anyway.

       popd [-p] [-l] [-n|-v] [+n]
               Without arguments, pops the directory stack and returns to  the
               new top directory.  With a number ‘+n’, discards the n’th entry
               in the stack.

               Finally, all forms of popd print  the  final  directory  stack,
               just  like  dirs.  The pushdsilent shell variable can be set to
               prevent  this  and  the  -p  flag  can  be  given  to  override
               pushdsilent.   The  -l, -n and -v flags have the same effect on
               popd as on dirs.  (+)

       printenv [name] (+)
               Prints the names and values of all  environment  variables  or,
               with name, the value of the environment variable name.

       pushd [-p] [-l] [-n|-v] [name|+n]
               Without  arguments,  exchanges  the  top  two  elements  of the
               directory  stack.   If  pushdtohome  is  set,   pushd   without
               arguments  does  ‘pushd ~’, like cd.  (+) With name, pushes the
               current working directory onto the directory stack and  changes
               to  name.   If  name  is  ‘-’ it is interpreted as the previous
               working directory (see Filename substitution).  (+) If  dunique
               is  set,  pushd  removes  any  instances of name from the stack
               before pushing it onto the stack.   (+)  With  a  number  ‘+n’,
               rotates the nth element of the directory stack around to be the
               top element and changes to it.  If dextract  is  set,  however,
               ‘pushd  +n’  extracts the nth directory, pushes it onto the top
               of the stack and changes to it.  (+)

               Finally, all forms of pushd print the  final  directory  stack,
               just  like  dirs.  The pushdsilent shell variable can be set to
               prevent  this  and  the  -p  flag  can  be  given  to  override
               pushdsilent.   The  -l, -n and -v flags have the same effect on
               pushd as on dirs.  (+)

       rehash  Causes  the  internal  hash  table  of  the  contents  of   the
               directories  in  the  path  variable to be recomputed.  This is
               needed if new commands are added to directories in  path  while
               you  are  logged  in.  This should be necessary only if you add
               commands to one of  your  own  directories,  or  if  a  systems
               programmer   changes   the   contents  of  one  of  the  system
               directories.  Also flushes the cache of home directories  built
               by tilde expansion.

       repeat count command
               The   specified   command,   which   is  subject  to  the  same
               restrictions as the command in the one line if statement above,
               is  executed count times.  I/O redirections occur exactly once,
               even if count is 0.

       rootnode //nodename (+)
               Changes the  rootnode  to  //nodename,  so  that  ‘/’  will  be
               interpreted as ‘//nodename’.  (Domain/OS only)

       sched (+)
       sched [+]hh:mm command (+)
       sched -n (+)
               The  first  form  prints  the  scheduled-event list.  The sched
               shell variable may be set to define the  format  in  which  the
               scheduled-event  list is printed.  The second form adds command
               to the scheduled-event list.  For example,

                   > sched 11:00 echo It\’s eleven o\’clock.

               causes the shell to echo ‘It’s eleven o’clock.’ at 11 AM.   The
               time may be in 12-hour AM/PM format

                   > sched 5pm set prompt=’[%h] It\’s after 5; go home: >’

               or may be relative to the current time:

                   > sched +2:15 /usr/lib/uucp/uucico -r1 -sother

               A  relative  time  specification may not use AM/PM format.  The
               third form removes item n from the event list:

                   > sched
                        1  Wed Apr  4 15:42  /usr/lib/uucp/uucico -r1 -sother
                        2  Wed Apr  4 17:00  set prompt=[%h] It’s after 5;  go
                   home: >
                   > sched -2
                   > sched
                        1  Wed Apr  4 15:42  /usr/lib/uucp/uucico -r1 -sother

               A  command  in the scheduled-event list is executed just before
               the first prompt is printed after the time when the command  is
               scheduled.   It  is  possible  to  miss the exact time when the
               command is to be run, but an overdue command  will  execute  at
               the  next prompt.  A command which comes due while the shell is
               waiting for  user  input  is  executed  immediately.   However,
               normal  operation  of  an  already-running  command will not be
               interrupted so that a scheduled-event list element may be  run.

               This  mechanism  is  similar to, but not the same as, the at(1)
               command on some Unix systems.  Its major disadvantage  is  that
               it  may  not  run a command at exactly the specified time.  Its
               major advantage is that because sched runs  directly  from  the
               shell,  it  has access to shell variables and other structures.
               This  provides  a  mechanism   for   changing   one’s   working
               environment based on the time of day.

       set
       set name ...
       set name=word ...
       set [-r] [-f|-l] name=(wordlist) ... (+)
       set name[index]=word ...
       set -r (+)
       set -r name ... (+)
       set -r name=word ... (+)
               The  first  form  of  the command prints the value of all shell
               variables.  Variables which contain more  than  a  single  word
               print  as a parenthesized word list.  The second form sets name
               to the null string.  The third form sets  name  to  the  single
               word.   The  fourth  form  sets  name  to  the list of words in
               wordlist.  In all cases  the  value  is  command  and  filename
               expanded.   If -r is specified, the value is set read-only.  If
               -f or -l are specified, set only  unique  words  keeping  their
               order.   -f  prefers the first occurrence of a word, and -l the
               last.  The fifth form sets the index’th component  of  name  to
               word;  this component must already exist.  The sixth form lists
               only the names of all shell variables that are read-only.   The
               seventh  form  makes  name  read-only,  whether or not it has a
               value.  The second form sets name  to  the  null  string.   The
               eighth  form is the same as the third form, but make name read-
               only at the same time.

               These arguments can be repeated to set  and/or  make  read-only
               multiple  variables  in  a  single set command.  Note, however,
               that variable expansion happens for all  arguments  before  any
               setting  occurs.   Note  also  that ‘=’ can be adjacent to both
               name and word or separated from both by whitespace, but  cannot
               be  adjacent  to  only  one  or  the other.  See also the unset
               builtin command.

       setenv [name [value]]
               Without  arguments,  prints  the  names  and  values   of   all
               environment   variables.   Given  name,  sets  the  environment
               variable name to value or, without value, to the null string.

       setpath path (+)
               Equivalent to setpath(1).  (Mach only)

       setspath LOCAL|site|cpu ... (+)
               Sets the system execution path.  (TCF only)

       settc cap value (+)
               Tells the shell to believe that the terminal capability cap (as
               defined in termcap(5)) has the value value.  No sanity checking
               is done.  Concept terminal users may have to ‘settc xn  no’  to
               get proper wrapping at the rightmost column.

       setty [-d|-q|-x] [-a] [[+|-]mode] (+)
               Controls  which  tty  modes (see Terminal management) the shell
               does not allow to change.  -d, -q or -x tells setty to  act  on
               the ‘edit’, ‘quote’ or ‘execute’ set of tty modes respectively;
               without -d, -q or -x, ‘execute’ is used.

               Without other arguments, setty lists the modes  in  the  chosen
               set  which  are  fixed  on  (‘+mode’)  or  off  (‘-mode’).  The
               available modes, and thus the  display,  vary  from  system  to
               system.  With -a, lists all tty modes in the chosen set whether
               or not they are fixed.  With +mode, -mode or mode,  fixes  mode
               on  or off or removes control from mode in the chosen set.  For
               example, ‘setty +echok echoe’ fixes ‘echok’ mode on and  allows
               commands to turn ‘echoe’ mode on or off, both when the shell is
               executing commands.

       setxvers [string] (+)
               Set the experimental version prefix to string, or removes it if
               string is omitted.  (TCF only)

       shift [variable]
               Without  arguments,  discards argv[1] and shifts the members of
               argv to the left.  It is an error for argv not to be set or  to
               have  less than one word as value.  With variable, performs the
               same function on variable.

       source [-h] name [args ...]
               The shell reads and executes commands from name.  The  commands
               are  not  placed  on  the history list.  If any args are given,
               they are placed in argv.  (+) source commands may be nested; if
               they  are  nested  too  deeply  the  shell  may run out of file
               descriptors.  An error in a source at any level terminates  all
               nested  source  commands.   With -h, commands are placed on the
               history list instead of being executed, much like ‘history -L’.

       stop %job|pid ...
               Stops  the  specified  jobs or processes which are executing in
               the background.  job may be a number, a string, ‘’, ‘%’, ‘+’ or
               ‘-’  as  described under Jobs.  There is no default job; saying
               just ‘stop’ does not stop the current job.

       suspend Causes the shell to stop in its tracks, much as if it had  been
               sent  a  stop  signal with ^Z.  This is most often used to stop
               shells started by su(1).

       switch (string)
       case str1:
           ...
           breaksw
       ...
       default:
           ...
           breaksw
       endsw   Each case label is successively matched, against the  specified
               string  which is first command and filename expanded.  The file
               metacharacters ‘*’, ‘?’ and ‘[...]’  may be used  in  the  case
               labels,  which  are  variable  expanded.  If none of the labels
               match before a ‘default’ label is  found,  then  the  execution
               begins  after  the  default  label.   Each  case  label and the
               default label must appear at the  beginning  of  a  line.   The
               command  breaksw  causes execution to continue after the endsw.
               Otherwise control may fall  through  case  labels  and  default
               labels  as  in C.  If no label matches and there is no default,
               execution continues after the endsw.

       telltc (+)
               Lists the values of all terminal capabilities (see termcap(5)).

       termname [terminal type] (+)
               Tests  if  terminal  type  (or  the current value of TERM if no
               terminal type is given) has an entry in the hosts termcap(5) or
               terminfo(5)  database.  Prints  the terminal type to stdout and
               returns 0 if an entry is present otherwise returns 1.

       time [command]
               Executes command (which must be a simple command, not an alias,
               a pipeline, a command list or a parenthesized command list) and
               prints a time summary as described under the time variable.  If
               necessary,  an  extra  shell  is  created  to  print  the  time
               statistic when the command completes.  Without command,  prints
               a time summary for the current shell and its children.

       umask [value]
               Sets  the file creation mask to value, which is given in octal.
               Common values for the mask are 002, giving all  access  to  the
               group  and  read  and execute access to others, and 022, giving
               read and execute access  to  the  group  and  others.   Without
               value, prints the current file creation mask.

       unalias pattern
               Removes  all  aliases  whose  names match pattern.  ‘unalias *’
               thus removes all aliases.  It is not an error for nothing to be
               unaliased.

       uncomplete pattern (+)
               Removes all completions whose names match pattern.  ‘uncomplete
               *’ thus removes all  completions.   It  is  not  an  error  for
               nothing to be uncompleted.

       unhash  Disables  use  of  the internal hash table to speed location of
               executed programs.

       universe universe (+)
               Sets the universe to universe.  (Masscomp/RTU only)

       unlimit [-h] [resource]
               Removes the limitation  on  resource  or,  if  no  resource  is
               specified,    all   resource   limitations.    With   -h,   the
               corresponding hard limits are removed.  Only the super-user may
               do this.  Note that unlimit may not exit successful, since most
               systems do not allow descriptors to be unlimited.

       unset pattern
               Removes all variables whose names match  pattern,  unless  they
               are  read-only.   ‘unset  *’  thus removes all variables unless
               they are read-only; this is a bad idea.  It is not an error for
               nothing to be unset.

       unsetenv pattern
               Removes  all  environment  variables whose names match pattern.
               ‘unsetenv *’ thus removes all environment variables; this is  a
               bad idea.  It is not an error for nothing to be unsetenved.

       ver [systype [command]] (+)
               Without  arguments, prints SYSTYPE.  With systype, sets SYSTYPE
               to systype.  With systype and command, executes  command  under
               systype.   systype  may  be  ‘bsd4.3’  or ‘sys5.3’.  (Domain/OS
               only)

       wait    The shell waits for all  background  jobs.   If  the  shell  is
               interactive,  an  interrupt will disrupt the wait and cause the
               shell to print the names and job  numbers  of  all  outstanding
               jobs.

       warp universe (+)
               Sets the universe to universe.  (Convex/OS only)

       watchlog (+)
               An   alternate   name  for  the  log  builtin  command  (q.v.).
               Available only if the shell was so compiled;  see  the  version
               shell variable.

       where command (+)
               Reports  all  known  instances  of  command, including aliases,
               builtins and executables in path.

       which command (+)
               Displays the command that will be executed by the  shell  after
               substitutions,  path  searching,  etc.   The builtin command is
               just like which(1), but it correctly reports tcsh  aliases  and
               builtins  and  is  10 to 100 times faster.  See also the which-
               command editor command.

       while (expr)
       ...
       end     Executes the commands between the while and  the  matching  end
               while  expr  (an  expression,  as  described under Expressions)
               evaluates non-zero.  while and end must appear alone  on  their
               input  lines.   break  and continue may be used to terminate or
               continue the loop prematurely.  If the input is a terminal, the
               user  is  prompted  the  first  time  through  the loop as with
               foreach.

   Special aliases (+)
       If set, each of these aliases executes automatically at  the  indicated
       time.  They are all initially undefined.

       beepcmd Runs when the shell wants to ring the terminal bell.

       cwdcmd  Runs  after every change of working directory.  For example, if
               the user is working on an X window system using xterm(1) and  a
               re-parenting  window  manager  that supports title bars such as
               twm(1) and does

                   > alias cwdcmd  ’echo -n "^[]2;${HOST}:$cwd ^G"’

               then the shell will change the title of the running xterm(1) to
               be  the name of the host, a colon, and the full current working
               directory.  A fancier way to do that is

                   >          alias          cwdcmd          ’echo          -n
                   "^[]2;${HOST}:$cwd^G^[]1;${HOST}^G"’

               This  will  put the hostname and working directory on the title
               bar but only the hostname in the icon manager menu.

               Note that putting a cd, pushd or popd in cwdcmd  may  cause  an
               infinite loop.  It is the author’s opinion that anyone doing so
               will get what they deserve.

       jobcmd  Runs before each command gets executed,  or  when  the  command
               changes  state.   This  is  similar to postcmd, but it does not
               print builtins.

                   > alias jobcmd  ’echo -n "^[]2\;\!#^G"’

               then executing vi foo.c will put  the  command  string  in  the
               xterm title bar.

       helpcommand
               Invoked  by  the run-help editor command.  The command name for
               which help is sought is passed as sole argument.  For  example,
               if one does

                   > alias helpcommand ’\!:1 --help’

               then  the  help  display of the command itself will be invoked,
               using the GNU help calling convention.  Currently there  is  no
               easy  way to account for various calling conventions (e.g., the
               customary Unix ‘-h’), except by using a table of many commands.

       periodic
               Runs  every  tperiod minutes.  This provides a convenient means
               for checking on common but infrequent changes such as new mail.
               For example, if one does

                   > set tperiod = 30
                   > alias periodic checknews

               then  the  checknews(1)  program  runs  every  30  minutes.  If
               periodic is set but tperiod is unset  or  set  to  0,  periodic
               behaves like precmd.

       precmd  Runs  just  before each prompt is printed.  For example, if one
               does

                   > alias precmd date

               then date(1) runs  just  before  the  shell  prompts  for  each
               command.   There are no limits on what precmd can be set to do,
               but discretion should be used.

       postcmd Runs before each command gets executed.

                   > alias postcmd  ’echo -n "^[]2\;\!#^G"’

               then executing vi foo.c will put  the  command  string  in  the
               xterm title bar.

       shell   Specifies  the  interpreter for executable scripts which do not
               themselves specify an interpreter.  The first word should be  a
               full  path name to the desired interpreter (e.g., ‘/bin/csh’ or
               ‘/usr/local/bin/tcsh’).

   Special shell variables
       The variables described in this section have  special  meaning  to  the
       shell.

       The  shell  sets  addsuffix,  argv,  autologout,  csubstnonl,  command,
       echo_style,  edit,  gid,  group,  home,  loginsh,  oid,  path,  prompt,
       prompt2,  prompt3, shell, shlvl, tcsh, term, tty, uid, user and version
       at startup; they do not change thereafter unless changed by  the  user.
       The  shell  updates  cwd,  dirstack, owd and status when necessary, and
       sets logout on logout.

       The shell synchronizes afsuser, group, home, path, shlvl, term and user
       with  the  environment  variables  of  the  same  names:  whenever  the
       environment variable changes the shell changes the corresponding  shell
       variable  to  match  (unless  the shell variable is read-only) and vice
       versa.  Note that although cwd and PWD have  identical  meanings,  they
       are  not  synchronized in this manner, and that the shell automatically
       interconverts the different formats of path and PATH.

       addsuffix (+)
               If set, filename completion adds ‘/’ to the end of  directories
               and  a  space  to the end of normal files when they are matched
               exactly.  Set by default.

       afsuser (+)
               If set, autologout’s autolock feature uses its value instead of
               the local username for kerberos authentication.

       ampm (+)
               If set, all times are shown in 12-hour AM/PM format.

       argv    The  arguments  to  the shell.  Positional parameters are taken
               from argv, i.e., ‘$1’ is replaced by ‘$argv[1]’, etc.   Set  by
               default, but usually empty in interactive shells.

       autocorrect (+)
               If  set, the spell-word editor command is invoked automatically
               before each completion attempt.

       autoexpand (+)
               If  set,  the  expand-history   editor   command   is   invoked
               automatically before each completion attempt.

       autolist (+)
               If set, possibilities are listed after an ambiguous completion.
               If set to ‘ambiguous’, possibilities are listed  only  when  no
               new characters are added by completion.

       autologout (+)
               The  first  word  is the number of minutes of inactivity before
               automatic logout.  The optional second word is  the  number  of
               minutes of inactivity before automatic locking.  When the shell
               automatically logs  out,  it  prints  ‘auto-logout’,  sets  the
               variable  logout  to  ‘automatic’  and  exits.   When the shell
               automatically locks, the user is required to enter his password
               to   continue  working.   Five  incorrect  attempts  result  in
               automatic logout.  Set  to  ‘60’  (automatic  logout  after  60
               minutes,  and  no  locking)  by  default in login and superuser
               shells, but not if the shell  thinks  it  is  running  under  a
               window  system (i.e., the DISPLAY environment variable is set),
               the tty is a pseudo-tty (pty) or the shell was not so  compiled
               (see  the  version  shell  variable).  See also the afsuser and
               logout shell variables.

       backslash_quote (+)
               If set, backslashes (‘\’) always quote ‘\’, ‘’’, and ‘"’.  This
               may  make complex quoting tasks easier, but it can cause syntax
               errors in csh(1) scripts.

       catalog The file name  of  the  message  catalog.   If  set,  tcsh  use
               ‘tcsh.${catalog}’  as  a  message  catalog  instead  of default
               ‘tcsh’.

       cdpath  A  list  of  directories  in  which  cd   should   search   for
               subdirectories if they aren’t found in the current directory.

       color   If  set,  it  enables color display for the builtin ls-F and it
               passes --color=auto to ls.  Alternatively, it  can  be  set  to
               only  ls-F  or  only  ls  to  enable color to only one command.
               Setting it to nothing is equivalent to setting it to (ls-F ls).

       colorcat
               If set, it enables color escape sequence for NLS message files.
               And display colorful NLS messages.

       command (+)
               If set, the command which was passed to the shell with  the  -c
               flag (q.v.).

       complete (+)
               If  set  to  ‘enhance’,  completion  1)  ignores  case  and  2)
               considers periods, hyphens and underscores (‘.’, ‘-’  and  ‘_’)
               to  be  word  separators  and  hyphens  and  underscores  to be
               equivalent. If set to ‘igncase’, the  completion  becomes  case
               insensitive.

       continue (+)
               If  set  to  a  list  of  commands, the shell will continue the
               listed commands, instead of starting a new one.

       continue_args (+)
               Same as continue, but the shell will execute:

                   echo ‘pwd‘ $argv > ~/.<cmd>_pause; %<cmd>

       correct (+)
               If set to ‘cmd’, commands are automatically spelling-corrected.
               If set to ‘complete’, commands are automatically completed.  If
               set to ‘all’, the entire command line is corrected.

       csubstnonl (+)
               If set, newlines and carriage returns in  command  substitution
               are replaced by spaces.  Set by default.

       cwd     The  full  pathname  of  the  current  directory.  See also the
               dirstack and owd shell variables.

       dextract (+)
               If  set,  ‘pushd  +n’  extracts  the  nth  directory  from  the
               directory stack rather than rotating it to the top.

       dirsfile (+)
               The  default location in which ‘dirs -S’ and ‘dirs -L’ look for
               a history file.  If unset, ~/.cshdirs is  used.   Because  only
               ~/.tcshrc  is  normally  sourced  before  ~/.cshdirs,  dirsfile
               should be set in ~/.tcshrc rather than ~/.login.

       dirstack (+)
               An array  of  all  the  directories  on  the  directory  stack.
               ‘$dirstack[1]’ is the current working directory, ‘$dirstack[2]’
               the first directory on the stack, etc.  Note that  the  current
               working directory is ‘$dirstack[1]’ but ‘=0’ in directory stack
               substitutions, etc.  One can change the  stack  arbitrarily  by
               setting  dirstack,  but  the first element (the current working
               directory) is always correct.  See also the cwd and  owd  shell
               variables.

       dspmbyte (+)
               Has an affect iff ’dspm’ is listed as part of the version shell
               variable.  If set to ‘euc’, it enables display and editing EUC-
               kanji(Japanese) code.  If set to ‘sjis’, it enables display and
               editing Shift-JIS(Japanese) code.  If set to ‘big5’, it enables
               display  and  editing Big5(Chinese) code.  If set to ‘utf8’, it
               enables display and editing Utf8(Unicode) code.  If set to  the
               following  format,  it  enables display and editing of original
               multi-byte code format:

                   > set dspmbyte = 0000....(256 bytes)....0000

               The table requires just  256  bytes.   Each  character  of  256
               characters  corresponds (from left to right) to the ASCII codes
               0x00, 0x01, ... 0xff.  Each character is set  to  number  0,1,2
               and 3.  Each number has the following meaning:
                 0 ... not used for multi-byte characters.
                 1 ... used for the first byte of a multi-byte character.
                 2 ... used for the second byte of a multi-byte character.
                 3  ...  used  for  both  the  first byte and second byte of a
               multi-byte character.

                 Example:
               If set to ‘001322’, the first  character  (means  0x00  of  the
               ASCII code) and second character (means 0x01 of ASCII code) are
               set to ‘0’.  Then, it is not used  for  multi-byte  characters.
               The  3rd  character (0x02) is set to ’1’, indicating that it is
               used for the first byte of a  multi-byte  character.   The  4th
               character(0x03) is set ’3’.  It is used for both the first byte
               and the second byte of a multi-byte character.  The 5th and 6th
               characters (0x04,0x05) are set to ’2’, indicating that they are
               used for the second byte of a multi-byte character.

               The GNU fileutils  version  of  ls  cannot  display  multi-byte
               filenames  without  the  -N  ( --literal ) option.   If you are
               using this version, set the second word of  dspmbyte  to  "ls".
               If  not,  for  example,  "ls-F  -l"  cannot  display multi-byte
               filenames.

                 Note:
               This variable can only be used if KANJI and DSPMBYTE  has  been
               defined at compile time.

       dunique (+)
               If  set,  pushd  removes  any  instances of name from the stack
               before pushing it onto the stack.

       echo    If set, each command with its arguments is echoed  just  before
               it  is executed.  For non-builtin commands all expansions occur
               before echoing.  Builtin commands are echoed before command and
               filename  substitution,  because  these  substitutions are then
               done selectively.  Set by the -x command line option.

       echo_style (+)
               The style of the echo builtin.  May be set to

               bsd     Don’t echo a newline if the first argument is ‘-n’.
               sysv    Recognize backslashed escape sequences in echo strings.
               both    Recognize  both  the  ‘-n’  flag and backslashed escape
                       sequences; the default.
               none    Recognize neither.

               Set by default to the local system default.  The BSD and System
               V  options  are  described  in  the  echo(1)  man  pages on the
               appropriate systems.

       edit (+)
               If set, the command-line editor is used.   Set  by  default  in
               interactive shells.

       ellipsis (+)
               If set, the ‘%c’/‘%.’ and ‘%C’ prompt sequences (see the prompt
               shell variable) indicate skipped directories with  an  ellipsis
               (‘...’)  instead of ‘/<skipped>’.

       fignore (+)
               Lists file name suffixes to be ignored by completion.

       filec   In tcsh, completion is always used and this variable is ignored
               by  default.  If  edit  is  unset,  then  the  traditional  csh
               completion  is  used.   If  set  in csh, filename completion is
               used.

       gid (+) The user’s real group ID.

       group (+)
               The user’s group name.

       histchars
               A string value  determining  the  characters  used  in  History
               substitution  (q.v.).  The first character of its value is used
               as the history substitution character,  replacing  the  default
               character  ‘!’.  The second character of its value replaces the
               character ‘^’ in quick substitutions.

       histdup (+)
               Controls handling of duplicate entries in the history list.  If
               set  to  ‘all’  only  unique  history events are entered in the
               history list.  If set to ‘prev’ and the last history  event  is
               the  same  as  the current command, then the current command is
               not entered in the history.  If set to  ‘erase’  and  the  same
               event  is found in the history list, that old event gets erased
               and the current one gets inserted.  Note that  the  ‘prev’  and
               ‘all’ options renumber history events so there are no gaps.

       histfile (+)
               The  default  location  in  which ‘history -S’ and ‘history -L’
               look for  a  history  file.   If  unset,  ~/.history  is  used.
               histfile is useful when sharing the same home directory between
               different  machines,  or  when  saving  separate  histories  on
               different   terminals.   Because  only  ~/.tcshrc  is  normally
               sourced before ~/.history, histfile should be set in  ~/.tcshrc
               rather than ~/.login.

       histlit (+)
               If  set, builtin and editor commands and the savehist mechanism
               use the literal (unexpanded) form of lines in the history list.
               See also the toggle-literal-history editor command.

       history The  first word indicates the number of history events to save.
               The optional second word (+)  indicates  the  format  in  which
               history  is printed; if not given, ‘%h\t%T\t%R\n’ is used.  The
               format sequences are described below  under  prompt;  note  the
               variable meaning of ‘%R’.  Set to ‘100’ by default.

       home    Initialized to the home directory of the invoker.  The filename
               expansion of ‘~’ refers to this variable.

       ignoreeof
               If set to the empty string or ‘0’ and the  input  device  is  a
               terminal,  the  end-of-file  command  (usually generated by the
               user by typing ‘^D’ on an empty line) causes the shell to print
               ‘Use  "exit" to leave tcsh.’ instead of exiting.  This prevents
               the shell from accidentally being  killed.   Historically  this
               setting  exited  after  26  successive  EOF’s to avoid infinite
               loops.  If set  to  a  number  n,  the  shell  ignores  n  -  1
               consecutive  end-of-files  and exits on the nth.  (+) If unset,
               ‘1’ is used, i.e., the shell exits on a single ‘^D’.

       implicitcd (+)
               If set, the shell treats a directory name typed as a command as
               though  it  were a request to change to that directory.  If set
               to verbose, the change of directory is echoed to  the  standard
               output.   This  behavior  is inhibited in non-interactive shell
               scripts, or for  command  strings  with  more  than  one  word.
               Changing directory takes precedence over executing a like-named
               command, but it is done after alias substitutions.   Tilde  and
               variable expansions work as expected.

       inputmode (+)
               If  set  to  ‘insert’ or ‘overwrite’, puts the editor into that
               input mode at the beginning of each line.

       killdup (+)
               Controls handling of duplicate entries in the  kill  ring.   If
               set  to ‘all’ only unique strings are entered in the kill ring.
               If set to ‘prev’ and the last killed string is the same as  the
               current  killed  string, then the current string is not entered
               in the ring.  If set to ‘erase’ and the same string is found in
               the  kill ring, the old string is erased and the current one is
               inserted.

       killring (+)
               Indicates the number of killed strings to keep in memory.   Set
               to  ‘30’  by  default.   If  unset or set to less than ‘2’, the
               shell will only keep the most recently killed string.   Strings
               are  put  in  the  killring  by the editor commands that delete
               (kill) strings of text, e.g.  backward-delete-word,  kill-line,
               etc,  as  well  as  the  copy-region-as-kill command.  The yank
               editor command will yank the most recently killed  string  into
               the  command-line,  while yank-pop (see Editor commands) can be
               used to yank earlier killed strings.

       listflags (+)
               If set to ‘x’, ‘a’ or ‘A’, or any  combination  thereof  (e.g.,
               ‘xA’),  they  are used as flags to ls-F, making it act like ‘ls
               -xF’, ‘ls -Fa’, ‘ls -FA’ or a combination  (e.g.,  ‘ls  -FxA’):
               ‘a’  shows all files (even if they start with a ‘.’), ‘A’ shows
               all files but ‘.’ and ‘..’, and ‘x’  sorts  across  instead  of
               down.   If  the  second word of listflags is set, it is used as
               the path to ‘ls(1)’.

       listjobs (+)
               If set, all jobs are listed when a job is suspended.  If set to
               ‘long’, the listing is in long format.

       listlinks (+)
               If  set,  the  ls-F  builtin  command shows the type of file to
               which each symbolic link points.

       listmax (+)
               The maximum number  of  items  which  the  list-choices  editor
               command will list without asking first.

       listmaxrows (+)
               The  maximum  number  of  rows  of items which the list-choices
               editor command will list without asking first.

       loginsh (+)
               Set by the shell if it is a login shell.  Setting or  unsetting
               it within a shell has no effect.  See also shlvl.

       logout (+)
               Set   by   the  shell  to  ‘normal’  before  a  normal  logout,
               ‘automatic’ before an automatic logout,  and  ‘hangup’  if  the
               shell was killed by a hangup signal (see Signal handling).  See
               also the autologout shell variable.

       mail    The names of the files or directories  to  check  for  incoming
               mail,  separated  by  whitespace,  and optionally preceded by a
               numeric word.  Before each prompt, if 10  minutes  have  passed
               since  the last check, the shell checks each file and says ‘You
               have new mail.’ (or, if mail contains multiple files, ‘You have
               new  mail  in  name.’)  if the filesize is greater than zero in
               size and has a modification time greater than its access  time.

               If  you  are  in  a  login shell, then no mail file is reported
               unless it has been  modified  after  the  time  the  shell  has
               started  up,  to  prevent  redundant notifications.  Most login
               programs will tell you whether or not you have  mail  when  you
               log in.

               If  a  file  specified  in  mail is a directory, the shell will
               count each file within that directory as  a  separate  message,
               and  will  report  ‘You  have n mails.’ or ‘You have n mails in
               name.’  as  appropriate.   This   functionality   is   provided
               primarily  for  those  systems which store mail in this manner,
               such as the Andrew Mail System.

               If the first word of mail is numeric it is taken as a different
               mail checking interval, in seconds.

               Under  very  rare circumstances, the shell may report ‘You have
               mail.’ instead of ‘You have new mail.’

       matchbeep (+)
               If  set  to  ‘never’,  completion  never  beeps.   If  set   to
               ‘nomatch’,  it  beeps  only  when there is no match.  If set to
               ‘ambiguous’, it beeps when there are multiple matches.  If  set
               to  ‘notunique’,  it  beeps  when  there is one exact and other
               longer matches.  If unset, ‘ambiguous’ is used.

       nobeep (+)
               If set, beeping is completely disabled.  See also  visiblebell.

       noclobber
               If set, restrictions are placed on output redirection to insure
               that  files  are  not  accidentally  destroyed  and  that  ‘>>’
               redirections  refer  to  existing  files,  as  described in the
               Input/output section.

       noding  If set, disable the printing of  ‘DING!’  in  the  prompt  time
               specifiers at the change of hour.

       noglob  If  set, Filename substitution and Directory stack substitution
               (q.v.) are inhibited.  This is most  useful  in  shell  scripts
               which  do not deal with filenames, or after a list of filenames
               has been obtained and further expansions are not desirable.

       nokanji (+)
               If set and the shell supports  Kanji  (see  the  version  shell
               variable), it is disabled so that the meta key can be used.

       nonomatch
               If set, a Filename substitution or Directory stack substitution
               (q.v.)  which  does  not  match  any  existing  files  is  left
               untouched  rather  than causing an error.  It is still an error
               for the substitution to be  malformed,  e.g.,  ‘echo  [’  still
               gives an error.

       nostat (+)
               A   list   of   directories   (or   glob-patterns  which  match
               directories; see Filename  substitution)  that  should  not  be
               stat(2)ed  during a completion operation.  This is usually used
               to exclude directories which take too much time to stat(2), for
               example /afs.

       notify  If  set,  the  shell  announces job completions asynchronously.
               The default is to present job completions just before  printing
               a prompt.

       oid (+) The user’s real organization ID.  (Domain/OS only)

       owd (+) The old working directory, equivalent to the ‘-’ used by cd and
               pushd.  See also the cwd and dirstack shell variables.

       path    A list of directories in which to look for executable commands.
               A  null  word  specifies the current directory.  If there is no
               path variable then only full path names will execute.  path  is
               set  by the shell at startup from the PATH environment variable
               or, if PATH does  not  exist,  to  a  system-dependent  default
               something  like  ‘(/usr/local/bin  /usr/bsd  /bin /usr/bin .)’.
               The shell may put ‘.’ first or last in path or omit it entirely
               depending  on  how  it  was  compiled;  see  the  version shell
               variable.  A shell which is given neither the  -c  nor  the  -t
               option  hashes  the  contents  of the directories in path after
               reading ~/.tcshrc and each time path is reset.  If one  adds  a
               new  command  to a directory in path while the shell is active,
               one may need to do a rehash for the shell to find it.

       printexitvalue (+)
               If set and an interactive program exits with a non-zero status,
               the shell prints ‘Exit status’.

       prompt  The  string  which  is printed before reading each command from
               the  terminal.   prompt  may  include  any  of  the   following
               formatting  sequences  (+),  which  are  replaced  by the given
               information:

               %/  The current working directory.
               %~  The  current  working  directory,  but  with   one’s   home
                   directory   represented   by  ‘~’  and  other  users’  home
                   directories  represented  by  ‘~user’   as   per   Filename
                   substitution.   ‘~user’  substitution  happens  only if the
                   shell has already used ‘~user’ in a pathname in the current
                   session.
               %c[[0]n], %.[[0]n]
                   The trailing component of the current working directory, or
                   n trailing components if a digit n is given.  If  n  begins
                   with  ‘0’,  the  number  of  skipped components precede the
                   trailing component(s) in the  format  ‘/<skipped>trailing’.
                   If  the  ellipsis shell variable is set, skipped components
                   are  represented  by  an  ellipsis  so  the  whole  becomes
                   ‘...trailing’.   ‘~’ substitution is done as in ‘%~’ above,
                   but the ‘~’ component is  ignored  when  counting  trailing
                   components.
               %C  Like %c, but without ‘~’ substitution.
               %h, %!, !
                   The current history event number.
               %M  The full hostname.
               %m  The hostname up to the first ‘.’.
               %S (%s)
                   Start (stop) standout mode.
               %B (%b)
                   Start (stop) boldfacing mode.
               %U (%u)
                   Start (stop) underline mode.
               %t, %@
                   The time of day in 12-hour AM/PM format.
               %T  Like  ‘%t’,  but  in 24-hour format (but see the ampm shell
                   variable).
               %p  The ‘precise’ time of day in  12-hour  AM/PM  format,  with
                   seconds.
               %P  Like  ‘%p’,  but  in 24-hour format (but see the ampm shell
                   variable).
               \c  c is parsed as in bindkey.
               ^c  c is parsed as in bindkey.
               %%  A single ‘%’.
               %n  The user name.
               %j  The number of jobs.
               %d  The weekday in ‘Day’ format.
               %D  The day in ‘dd’ format.
               %w  The month in ‘Mon’ format.
               %W  The month in ‘mm’ format.
               %y  The year in ‘yy’ format.
               %Y  The year in ‘yyyy’ format.
               %l  The shell’s tty.
               %L  Clears from the end of the prompt to end of the display  or
                   the end of the line.
               %$  Expands  the shell or environment variable name immediately
                   after the ‘$’.
               %#  ‘>’ (or  the  first  character  of  the  promptchars  shell
                   variable) for normal users, ‘#’ (or the second character of
                   promptchars) for the superuser.
               %{string%}
                   Includes string as a literal escape sequence.  It should be
                   used only to change terminal attributes and should not move
                   the cursor location.  This cannot be the last  sequence  in
                   prompt.
               %?  The  return  code  of  the command executed just before the
                   prompt.
               %R  In prompt2, the status of  the  parser.   In  prompt3,  the
                   corrected string.  In history, the history string.

               ‘%B’,  ‘%S’, ‘%U’ and ‘%{string%}’ are available in only eight-
               bit-clean shells; see the version shell variable.

               The bold, standout and underline sequences are  often  used  to
               distinguish a superuser shell.  For example,

                   > set prompt = "%m [%h] %B[%@]%b [%/] you rang? "
                   tut [37] [2:54pm] [/usr/accts/sys] you rang? _

               If  ‘%t’,  ‘%@’, ‘%T’, ‘%p’, or ‘%P’ is used, and noding is not
               set, then print ‘DING!’ on  the  change  of  hour  (i.e,  ‘:00’
               minutes) instead of the actual time.

               Set by default to ‘%# ’ in interactive shells.

       prompt2 (+)
               The  string with which to prompt in while and foreach loops and
               after lines ending in ‘\’.  The same format  sequences  may  be
               used  as  in  prompt (q.v.); note the variable meaning of ‘%R’.
               Set by default to ‘%R? ’ in interactive shells.

       prompt3 (+)
               The string with  which  to  prompt  when  confirming  automatic
               spelling  correction.  The same format sequences may be used as
               in prompt (q.v.); note the variable meaning of  ‘%R’.   Set  by
               default to ‘CORRECT>%R (y|n|e|a)? ’ in interactive shells.

       promptchars (+)
               If  set  (to  a  two-character  string),  the  ‘%#’  formatting
               sequence in the prompt shell  variable  is  replaced  with  the
               first  character  for normal users and the second character for
               the superuser.

       pushdtohome (+)
               If set, pushd without arguments does ‘pushd ~’, like cd.

       pushdsilent (+)
               If set, pushd and popd do not print the directory stack.

       recexact (+)
               If set, completion completes on an exact match even if a longer
               match is possible.

       recognize_only_executables (+)
               If  set,  command  listing displays only files in the path that
               are executable.  Slow.

       rmstar (+)
               If set, the user is prompted before ‘rm *’ is executed.

       rprompt (+)
               The string to print on the right-hand side of the screen (after
               the  command  input)  when the prompt is being displayed on the
               left.  It recognizes the same formatting characters as  prompt.
               It  will  automatically disappear and reappear as necessary, to
               ensure that command input isn’t obscured, and will appear  only
               if  the  prompt, command input, and itself will fit together on
               the first line.  If  edit  isn’t  set,  then  rprompt  will  be
               printed after the prompt and before the command input.

       savedirs (+)
               If  set, the shell does ‘dirs -S’ before exiting.  If the first
               word is set to a number, at  most  that  many  directory  stack
               entries are saved.

       savehist
               If  set,  the  shell  does ‘history -S’ before exiting.  If the
               first word is set to a number, at  most  that  many  lines  are
               saved.  (The number must be less than or equal to history.)  If
               the second word is set to ‘merge’, the history list  is  merged
               with  the  existing  history  file  instead of replacing it (if
               there is one) and sorted by time  stamp  and  the  most  recent
               events are retained.  (+)

       sched (+)
               The  format in which the sched builtin command prints scheduled
               events; if not  given,  ‘%h\t%T\t%R\n’  is  used.   The  format
               sequences  are  described above under prompt; note the variable
               meaning of ‘%R’.

       shell   The file in which the shell resides.  This is used  in  forking
               shells  to  interpret  files  which  have execute bits set, but
               which are not executable by the system.  (See  the  description
               of  Builtin and non-builtin command execution.)  Initialized to
               the (system-dependent) home of the shell.

       shlvl (+)
               The number of nested shells.  Reset to 1 in login shells.   See
               also loginsh.

       status  The  status  returned  by  the  last command.  If it terminated
               abnormally, then 0200 is added to the status.  Builtin commands
               which  fail  return exit status ‘1’, all other builtin commands
               return status ‘0’.

       symlinks (+)
               Can be set to several different values to control symbolic link
               (‘symlink’) resolution:

               If  set to ‘chase’, whenever the current directory changes to a
               directory containing a symbolic link, it  is  expanded  to  the
               real name of the directory to which the link points.  This does
               not work for the user’s home directory; this is a bug.

               If set to ‘ignore’, the shell  tries  to  construct  a  current
               directory relative to the current directory before the link was
               crossed.  This means that cding through  a  symbolic  link  and
               then  ‘cd  ..’ing  returns one to the original directory.  This
               affects only builtin commands and filename completion.

               If set to ‘expand’, the shell tries to fix  symbolic  links  by
               actually  expanding arguments which look like path names.  This
               affects any command, not just  builtins.   Unfortunately,  this
               does  not  work  for hard-to-recognize filenames, such as those
               embedded in command options.  Expansion  may  be  prevented  by
               quoting.  While this setting is usually the most convenient, it
               is sometimes misleading and sometimes confusing when  it  fails
               to   recognize   an  argument  which  should  be  expanded.   A
               compromise is to  use  ‘ignore’  and  use  the  editor  command
               normalize-path (bound by default to ^X-n) when necessary.

               Some  examples  are  in  order.   First, let’s set up some play
               directories:

                   > cd /tmp
                   > mkdir from from/src to
                   > ln -s from/src to/dst

               Here’s the behavior with symlinks unset,

                   > cd /tmp/to/dst; echo $cwd
                   /tmp/to/dst
                   > cd ..; echo $cwd
                   /tmp/from

               here’s the behavior with symlinks set to ‘chase’,

                   > cd /tmp/to/dst; echo $cwd
                   /tmp/from/src
                   > cd ..; echo $cwd
                   /tmp/from

               here’s the behavior with symlinks set to ‘ignore’,

                   > cd /tmp/to/dst; echo $cwd
                   /tmp/to/dst
                   > cd ..; echo $cwd
                   /tmp/to

               and here’s the behavior with symlinks set to ‘expand’.

                   > cd /tmp/to/dst; echo $cwd
                   /tmp/to/dst
                   > cd ..; echo $cwd
                   /tmp/to
                   > cd /tmp/to/dst; echo $cwd
                   /tmp/to/dst
                   > cd ".."; echo $cwd
                   /tmp/from
                   > /bin/echo ..
                   /tmp/to
                   > /bin/echo ".."
                   ..

               Note that ‘expand’ expansion 1) works just  like  ‘ignore’  for
               builtins  like  cd,  2) is prevented by quoting, and 3) happens
               before filenames are passed to non-builtin commands.

       tcsh (+)
               The version number of the shell in the format ‘R.VV.PP’,  where
               ‘R’  is  the major release number, ‘VV’ the current version and
               ‘PP’ the patchlevel.

       term    The terminal type.  Usually set in ~/.login as described  under
               Startup and shutdown.

       time    If  set  to  a  number,  then  the time builtin (q.v.) executes
               automatically after each command which  takes  more  than  that
               many  CPU  seconds.  If there is a second word, it is used as a
               format string for the output of  the  time  builtin.   (u)  The
               following sequences may be used in the format string:

               %U  The time the process spent in user mode in cpu seconds.
               %S  The time the process spent in kernel mode in cpu seconds.
               %E  The elapsed (wall clock) time in seconds.
               %P  The CPU percentage computed as (%U + %S) / %E.
               %W  Number of times the process was swapped.
               %X  The average amount in (shared) text space used in Kbytes.
               %D  The  average  amount in (unshared) data/stack space used in
                   Kbytes.
               %K  The total space used (%X + %D) in Kbytes.
               %M  The maximum memory the process had in use at  any  time  in
                   Kbytes.
               %F  The  number of major page faults (page needed to be brought
                   from disk).
               %R  The number of minor page faults.
               %I  The number of input operations.
               %O  The number of output operations.
               %r  The number of socket messages received.
               %s  The number of socket messages sent.
               %k  The number of signals received.
               %w  The number of voluntary context switches (waits).
               %c  The number of involuntary context switches.

               Only the first four sequences are supported on systems  without
               BSD  resource limit functions.  The default time format is ‘%Uu
               %Ss %E %P %X+%Dk %I+%Oio %Fpf+%Ww’  for  systems  that  support
               resource  usage  reporting and ‘%Uu %Ss %E %P’ for systems that
               do not.

               Under Sequent’s DYNIX/ptx, %X,  %D,  %K,  %r  and  %s  are  not
               available, but the following additional sequences are:

               %Y  The number of system calls performed.
               %Z  The number of pages which are zero-filled on demand.
               %i  The  number  of  times  a  process’s  resident set size was
                   increased by the kernel.
               %d  The number of times  a  process’s  resident  set  size  was
                   decreased by the kernel.
               %l  The number of read system calls performed.
               %m  The number of write system calls performed.
               %p  The number of reads from raw disk devices.
               %q  The number of writes to raw disk devices.

               and  the  default  time  format  is  ‘%Uu  %Ss  %E  %P  %I+%Oio
               %Fpf+%Ww’.  Note that the CPU percentage  can  be  higher  than
               100% on multi-processors.

       tperiod (+)
               The  period,  in  minutes,  between  executions of the periodic
               special alias.

       tty (+) The name of the tty, or empty if not attached to one.

       uid (+) The user’s real user ID.

       user    The user’s login name.

       verbose If set, causes the words of each command to be  printed,  after
               history  substitution  (if  any).   Set  by the -v command line
               option.

       version (+)
               The version ID stamp.  It contains the shell’s  version  number
               (see  tcsh), origin, release date, vendor, operating system and
               machine (see VENDOR, OSTYPE and MACHTYPE) and a comma-separated
               list  of options which were set at compile time.  Options which
               are set by default in the distribution are noted.

               8b    The shell is eight bit clean; default
               7b    The shell is not eight bit clean
               wide  The shell is multibyte encoding clean (like UTF-8)
               nls   The system’s NLS is used; default for systems with NLS
               lf    Login shells execute  /etc/csh.login  before  instead  of
                     after /etc/csh.cshrc and ~/.login before instead of after
                     ~/.tcshrc and ~/.history.
               dl    ‘.’ is put last in path for security; default
               nd    ‘.’ is omitted from path for security
               vi    vi-style editing is the default rather than emacs
               dtr   Login shells drop DTR when exiting
               bye   bye is a synonym for logout and log is an alternate  name
                     for watchlog
               al    autologout is enabled; default
               kan   Kanji   is   used  if  appropriate  according  to  locale
                     settings, unless the nokanji shell variable is set
               sm    The system’s malloc(3) is used
               hb    The ‘#!<program>  <args>’  convention  is  emulated  when
                     executing shell scripts
               ng    The newgrp builtin is available
               rh    The  shell  attempts  to  set  the REMOTEHOST environment
                     variable
               afs   The shell verifies your password with the kerberos server
                     if   local   authentication  fails.   The  afsuser  shell
                     variable or the  AFSUSER  environment  variable  override
                     your local username if set.

               An  administrator  may  enter  additional  strings  to indicate
               differences in the local version.

       visiblebell (+)
               If set, a screen flash is used rather than  the  audible  bell.
               See also nobeep.

       watch (+)
               A  list of user/terminal pairs to watch for logins and logouts.
               If either the user is ‘any’ all terminals are watched  for  the
               given  user  and  vice  versa.   Setting  watch  to ‘(any any)’
               watches all users and terminals.  For example,

                   set watch = (george ttyd1 any console $user any)

               reports activity of the user ‘george’ on ttyd1, any user on the
               console, and oneself (or a trespasser) on any terminal.

               Logins and logouts are checked every 10 minutes by default, but
               the first word of watch can be set to a number to  check  every
               so many minutes.  For example,

                   set watch = (1 any any)

               reports any login/logout once every minute.  For the impatient,
               the log builtin command triggers a watch report  at  any  time.
               All  current logins are reported (as with the log builtin) when
               watch is first set.

               The who shell variable controls the format of watch reports.

       who (+) The format string for watch messages.  The following  sequences
               are replaced by the given information:

               %n  The name of the user who logged in/out.
               %a  The  observed  action,  i.e.,  ‘logged on’, ‘logged off’ or
                   ‘replaced olduser on’.
               %l  The terminal (tty) on which the user logged in/out.
               %M  The full hostname of the remote host,  or  ‘local’  if  the
                   login/logout was from the local host.
               %m  The  hostname  of the remote host up to the first ‘.’.  The
                   full name is printed if it is an IP address or an X  Window
                   System display.

               %M  and  %m are available on only systems that store the remote
               hostname in /etc/utmp.  If unset, ‘%n has %a %l  from  %m.’  is
               used,  or  ‘%n  has  %a  %l.’  on systems which don’t store the
               remote hostname.

       wordchars (+)
               A list of non-alphanumeric characters to be considered part  of
               a   word   by  the  forward-word,  backward-word  etc.,  editor
               commands.  If unset, ‘*?_-.[]~=’ is used.

ENVIRONMENT

       AFSUSER (+)
               Equivalent to the afsuser shell variable.

       COLUMNS The  number  of  columns  in  the   terminal.    See   Terminal
               management.

       DISPLAY Used by X Window System (see X(1)).  If set, the shell does not
               set autologout (q.v.).

       EDITOR  The  pathname  to  a  default  editor.   See  also  the  VISUAL
               environment variable and the run-fg-editor editor command.

       GROUP (+)
               Equivalent to the group shell variable.

       HOME    Equivalent to the home shell variable.

       HOST (+)
               Initialized  to  the  name of the machine on which the shell is
               running, as determined by the gethostname(2) system call.

       HOSTTYPE (+)
               Initialized to the type  of  machine  on  which  the  shell  is
               running,  as  determined  at  compile  time.   This variable is
               obsolete and will be removed in a future version.

       HPATH (+)
               A colon-separated list of directories  in  which  the  run-help
               editor command looks for command documentation.

       LANG    Gives the preferred character environment.  See Native Language
               System support.

       LC_CTYPE
               If set, only ctype character handling is changed.   See  Native
               Language System support.

       LINES   The  number of lines in the terminal.  See Terminal management.

       LS_COLORS
               The format of this variable is reminiscent  of  the  termcap(5)
               file  format; a colon-separated list of expressions of the form
               "xx=string", where "xx" is a two-character variable name.   The
               variables with their associated defaults are:

                   no   0      Normal (non-filename) text
                   fi   0      Regular file
                   di   01;34  Directory
                   ln   01;36  Symbolic link
                   pi   33     Named pipe (FIFO)
                   so   01;35  Socket
                   do   01;35  Door
                   bd   01;33  Block device
                   cd   01;32  Character device
                   ex   01;32  Executable file
                   mi   (none) Missing file (defaults to fi)
                   or   (none) Orphaned symbolic link (defaults to ln)
                   lc   ^[[    Left code
                   rc   m      Right code
                   ec   (none) End code (replaces lc+no+rc)

               You  need to include only the variables you want to change from
               the default.

               File names can also be colorized based on  filename  extension.
               This  is  specified  in the LS_COLORS variable using the syntax
               "*ext=string".  For example, using ISO 6429 codes, to color all
               C-language  source files blue you would specify "*.c=34".  This
               would color all files ending in .c in blue (34) color.

               Control characters can be  written  either  in  C-style-escaped
               notation,  or  in  stty-like  ^-notation.  The C-style notation
               adds ^[ for Escape, _ for a normal space character, and  ?  for
               Delete.   In  addition,  the ^[ escape character can be used to
               override the default interpretation of ^[, ^, : and =.

               Each file will be written as <lc> <color-code> <rc>  <filename>
               <ec>.   If  the  <ec> code is undefined, the sequence <lc> <no>
               <rc> will be used instead.  This is generally  more  convenient
               to  use,  but  less general.  The left, right and end codes are
               provided so you don’t have to type common parts over  and  over
               again  and  to  support weird terminals; you will generally not
               need to change them at all unless your terminal  does  not  use
               ISO 6429 color sequences but a different system.

               If your terminal does use ISO 6429 color codes, you can compose
               the type codes (i.e., all except the lc, rc, and ec codes) from
               numerical  commands  separated  by semicolons.  The most common
               commands are:

                       0   to restore default color
                       1   for brighter colors
                       4   for underlined text
                       5   for flashing text
                       30  for black foreground
                       31  for red foreground
                       32  for green foreground
                       33  for yellow (or brown) foreground
                       34  for blue foreground
                       35  for purple foreground
                       36  for cyan foreground
                       37  for white (or gray) foreground
                       40  for black background
                       41  for red background
                       42  for green background
                       43  for yellow (or brown) background
                       44  for blue background
                       45  for purple background
                       46  for cyan background
                       47  for white (or gray) background

               Not all commands will work on all systems or display devices.

               A few terminal programs do not recognize the default  end  code
               properly.   If all text gets colorized after you do a directory
               listing, try changing the  no  and  fi  codes  from  0  to  the
               numerical  codes for your standard fore- and background colors.

       MACHTYPE (+)
               The machine type (microprocessor class or  machine  model),  as
               determined at compile time.

       NOREBIND (+)
               If  set,  printable  characters are not rebound to self-insert-
               command.  See Native Language System support.

       OSTYPE (+)
               The operating system, as determined at compile time.

       PATH    A colon-separated list of directories  in  which  to  look  for
               executables.   Equivalent  to the path shell variable, but in a
               different format.

       PWD (+) Equivalent to the cwd shell variable, but not  synchronized  to
               it; updated only after an actual directory change.

       REMOTEHOST (+)
               The host from which the user has logged in remotely, if this is
               the case and the shell is able to determine it.   Set  only  if
               the shell was so compiled; see the version shell variable.

       SHLVL (+)
               Equivalent to the shlvl shell variable.

       SYSTYPE (+)
               The current system type.  (Domain/OS only)

       TERM    Equivalent to the term shell variable.

       TERMCAP The terminal capability string.  See Terminal management.

       USER    Equivalent to the user shell variable.

       VENDOR (+)
               The vendor, as determined at compile time.

       VISUAL  The  pathname  to  a  default full-screen editor.  See also the
               EDITOR  environment  variable  and  the  run-fg-editor   editor
               command.

FILES

       /etc/csh.cshrc  Read first by every shell.  ConvexOS, Stellix and Intel
                       use /etc/cshrc and  NeXTs  use  /etc/cshrc.std.   A/UX,
                       AMIX,  Cray  and IRIX have no equivalent in csh(1), but
                       read this file in tcsh anyway.  Solaris  2.x  does  not
                       have it either, but tcsh reads /etc/.cshrc.  (+)
       /etc/csh.login  Read  by  login shells after /etc/csh.cshrc.  ConvexOS,
                       Stellix   and   Intel   use   /etc/login,   NeXTs   use
                       /etc/login.std,  Solaris 2.x uses /etc/.login and A/UX,
                       AMIX, Cray and IRIX use /etc/cshrc.
       ~/.tcshrc (+)   Read  by  every  shell  after  /etc/csh.cshrc  or   its
                       equivalent.
       ~/.cshrc        Read  by every shell, if ~/.tcshrc doesn’t exist, after
                       /etc/csh.cshrc or its  equivalent.   This  manual  uses
                       ‘~/.tcshrc’  to mean ‘~/.tcshrc or, if ~/.tcshrc is not
                       found, ~/.cshrc’.
       ~/.history      Read by login shells after  ~/.tcshrc  if  savehist  is
                       set, but see also histfile.
       ~/.login        Read  by  login  shells  after ~/.tcshrc or ~/.history.
                       The shell may  be  compiled  to  read  ~/.login  before
                       instead  of  after  ~/.tcshrc  and  ~/.history; see the
                       version shell variable.
       ~/.cshdirs (+)  Read by login shells after ~/.login if savedirs is set,
                       but see also dirsfile.
       /etc/csh.logout Read  by login shells at logout.  ConvexOS, Stellix and
                       Intel use /etc/logout and  NeXTs  use  /etc/logout.std.
                       A/UX, AMIX, Cray and IRIX have no equivalent in csh(1),
                       but read this file in tcsh anyway.   Solaris  2.x  does
                       not have it either, but tcsh reads /etc/.logout.  (+)
       ~/.logout       Read by login shells at logout after /etc/csh.logout or
                       its equivalent.
       /bin/sh         Used to interpret shell scripts  not  starting  with  a
                       ‘#’.
       /tmp/sh*        Temporary file for ‘<<’.
       /etc/passwd     Source of home directories for ‘~name’ substitutions.

       The  order  in which startup files are read may differ if the shell was
       so compiled; see Startup and shutdown and the version shell variable.

NEW FEATURES (+)

       This manual describes tcsh as a single entity, but  experienced  csh(1)
       users will want to pay special attention to tcsh’s new features.

       A  command-line  editor,  which  supports  GNU Emacs or vi(1)-style key
       bindings.  See The command-line editor and Editor commands.

       Programmable, interactive word completion and listing.  See  Completion
       and listing and the complete and uncomplete builtin commands.

       Spelling correction (q.v.) of filenames, commands and variables.

       Editor  commands  (q.v.)  which  perform  other useful functions in the
       middle of typed commands, including  documentation  lookup  (run-help),
       quick  editor restarting (run-fg-editor) and command resolution (which-
       command).

       An enhanced history mechanism.  Events in the history  list  are  time-
       stamped.   See  also  the  history  command  and  its  associated shell
       variables, the previously undocumented  ‘#’  event  specifier  and  new
       modifiers  under History substitution, the *-history, history-search-*,
       i-search-*, vi-search-* and toggle-literal-history editor commands  and
       the histlit shell variable.

       Enhanced  directory  parsing and directory stack handling.  See the cd,
       pushd, popd and dirs commands and their associated shell variables, the
       description  of  Directory  stack  substitution,  the dirstack, owd and
       symlinks shell variables and the normalize-command  and  normalize-path
       editor commands.

       Negation in glob-patterns.  See Filename substitution.

       New  File  inquiry  operators  (q.v.) and a filetest builtin which uses
       them.

       A variety of Automatic, periodic  and  timed  events  (q.v.)  including
       scheduled  events,  special  aliases,  automatic  logout  and  terminal
       locking, command timing and watching for logins and logouts.

       Support for the Native Language  System  (see  Native  Language  System
       support),   OS  variant  features  (see  OS  variant  support  and  the
       echo_style shell variable) and  system-dependent  file  locations  (see
       FILES).

       Extensive terminal-management capabilities.  See Terminal management.

       New  builtin  commands including builtins, hup, ls-F, newgrp, printenv,
       which and where (q.v.).

       New variables that make useful  information  easily  available  to  the
       shell.   See  the  gid, loginsh, oid, shlvl, tcsh, tty, uid and version
       shell variables and the HOST, REMOTEHOST, VENDOR, OSTYPE  and  MACHTYPE
       environment variables.

       A new syntax for including useful information in the prompt string (see
       prompt).  and special prompts for loops and  spelling  correction  (see
       prompt2 and prompt3).

       Read-only variables.  See Variable substitution.

BUGS

       When  a  suspended command is restarted, the shell prints the directory
       it started in if this is different from the  current  directory.   This
       can be misleading (i.e., wrong) as the job may have changed directories
       internally.

       Shell  builtin  functions  are  not   stoppable/restartable.    Command
       sequences  of the form ‘a ; b ; c’ are also not handled gracefully when
       stopping is attempted.   If  you  suspend  ‘b’,  the  shell  will  then
       immediately  execute  ‘c’.   This  is  especially  noticeable  if  this
       expansion results from an alias.  It suffices to place the sequence  of
       commands in ()’s to force it to a subshell, i.e., ‘( a ; b ; c )’.

       Control  over  tty  output  after  processes  are started is primitive;
       perhaps this will inspire someone to work on a  good  virtual  terminal
       interface.   In  a  virtual  terminal  interface  much more interesting
       things could be done with output control.

       Alias substitution is  most  often  used  to  clumsily  simulate  shell
       procedures; shell procedures should be provided rather than aliases.

       Commands  within  loops  are  not  placed in the history list.  Control
       structures should be parsed rather than being  recognized  as  built-in
       commands.   This would allow control commands to be placed anywhere, to
       be combined with ‘|’, and to be used with ‘&’ and ‘;’ metasyntax.

       foreach doesn’t ignore here documents when looking for its end.

       It should be possible to use the ‘:’ modifiers on the output of command
       substitutions.

       The  screen  update for lines longer than the screen width is very poor
       if the terminal cannot move the cursor up (i.e., terminal type ‘dumb’).

       HPATH and NOREBIND don’t need to be environment variables.

       Glob-patterns  which  do  not use ‘?’, ‘*’ or ‘[]’ or which use ‘{}’ or
       ‘~’ are not negated correctly.

       The single-command form of if  does  output  redirection  even  if  the
       expression is false and the command is not executed.

       ls-F includes file identification characters when sorting filenames and
       does not handle control characters in filenames  well.   It  cannot  be
       interrupted.

       Command substitution supports multiple commands and conditions, but not
       cycles or backward gotos.

       Report bugs at http://bugs.gw.com/, preferably with fixes.  If you want
       to  help  maintain  and  test tcsh, send mail to tcsh-request@mx.gw.com
       with the text ‘subscribe tcsh’ on a line by itself in the body.

THE T IN TCSH

       In  1964,  DEC  produced  the  PDP-6.   The  PDP-10  was  a  later  re-
       implementation.   It  was  re-christened the DECsystem-10 in 1970 or so
       when DEC brought out the second model, the KI10.

       TENEX was created at Bolt, Beranek & Newman (a Cambridge, Massachusetts
       think  tank)  in  1972  as an experiment in demand-paged virtual memory
       operating systems.  They built a new  pager  for  the  DEC  PDP-10  and
       created the OS to go with it.  It was extremely successful in academia.

       In 1975, DEC brought out a new model of  the  PDP-10,  the  KL10;  they
       intended  to have only a version of TENEX, which they had licensed from
       BBN, for the  new  box.   They  called  their  version  TOPS-20  (their
       capitalization is trademarked).  A lot of TOPS-10 users (‘The OPerating
       System for PDP-10’) objected; thus DEC found themselves supporting  two
       incompatible systems on the same hardware--but then there were 6 on the
       PDP-11!

       TENEX, and TOPS-20 to version 3, had command  completion  via  a  user-
       code-level subroutine library called ULTCMD.  With version 3, DEC moved
       all that capability and more into the monitor (‘kernel’  for  you  Unix
       types),  accessed by the COMND% JSYS (‘Jump to SYStem’ instruction, the
       supervisor call mechanism [are my IBM roots also showing?]).

       The creator of tcsh was impressed by this feature and several others of
       TENEX and TOPS-20, and created a version of csh which mimicked them.

LIMITATIONS

       Words can be no longer than 1024 characters.

       The system limits argument lists to 10240 characters.

       The  number of arguments to a command which involves filename expansion
       is limited to 1/6th the number of characters  allowed  in  an  argument
       list.

       Command  substitutions  may  substitute  no  more  characters  than are
       allowed in an argument list.

       To  detect  looping,  the  shell  restricts   the   number   of   alias
       substitutions on a single line to 20.

SEE ALSO

       csh(1),  emacs(1), ls(1), newgrp(1), sh(1), setpath(1), stty(1), su(1),
       tset(1),  vi(1),  x(1),  access(2),  execve(2),   fork(2),   killpg(2),
       pipe(2), setrlimit(2), sigvec(2), stat(2), umask(2), vfork(2), wait(2),
       malloc(3),  setlocale(3),  tty(4),  a.out(5),  termcap(5),  environ(7),
       termio(7), Introduction to the C Shell

VERSION

       This manual documents tcsh 6.14.00 (Astron) 2005-03-25.

AUTHORS

       William Joy
         Original author of csh(1)
       J.E. Kulp, IIASA, Laxenburg, Austria
         Job control and directory stack features
       Ken Greer, HP Labs, 1981
         File name completion
       Mike Ellis, Fairchild, 1983
         Command name recognition/completion
       Paul Placeway, Ohio State CIS Dept., 1983-1993
         Command  line  editor,  prompt routines, new glob syntax and numerous
         fixes and speedups
       Karl Kleinpaste, CCI 1983-4
         Special  aliases,  directory  stack  extraction  stuff,  login/logout
         watch, scheduled events, and the idea of the new prompt format
       Rayan Zachariassen, University of Toronto, 1984
         ls-F  and  which  builtins  and numerous bug fixes, modifications and
         speedups
       Chris Kingsley, Caltech
         Fast storage allocator routines
       Chris Grevstad, TRW, 1987
         Incorporated 4.3BSD csh into tcsh
       Christos S. Zoulas, Cornell U. EE Dept., 1987-94
         Ports  to  HPUX,  SVR2  and  SVR3,  a  SysV   version   of   getwd.c,
         SHORT_STRINGS support and a new version of sh.glob.c
       James J Dempsey, BBN, and Paul Placeway, OSU, 1988
         A/UX port
       Daniel Long, NNSC, 1988
         wordchars
       Patrick Wolfe, Kuck and Associates, Inc., 1988
         vi mode cleanup
       David C Lawrence, Rensselaer Polytechnic Institute, 1989
         autolist and ambiguous completion listing
       Alec Wolman, DEC, 1989
         Newlines in the prompt
       Matt Landau, BBN, 1989
         ~/.tcshrc
       Ray Moody, Purdue Physics, 1989
         Magic space bar history expansion
       Mordechai ????, Intel, 1989
         printprompt() fixes and additions
       Kazuhiro Honda, Dept. of Computer Science, Keio University, 1989
         Automatic spelling correction and prompt3
       Per Hedeland, Ellemtel, Sweden, 1990-
         Various bugfixes, improvements and manual updates
       Hans J. Albertsson (Sun Sweden)
         ampm, settc and telltc
       Michael Bloom
         Interrupt handling fixes
       Michael Fine, Digital Equipment Corp
         Extended key support
       Eric Schnoebelen, Convex, 1990
         Convex  support, lots of csh bug fixes, save and restore of directory
         stack
       Ron Flax, Apple, 1990
         A/UX 2.0 (re)port
       Dan Oscarsson, LTH Sweden, 1990
         NLS support and simulated NLS support for non NLS sites, fixes
       Johan Widen, SICS Sweden, 1990
         shlvl, Mach support, correct-line, 8-bit printing
       Matt Day, Sanyo Icon, 1990
         POSIX termio support, SysV limit fixes
       Jaap Vermeulen, Sequent, 1990-91
         Vi mode fixes, expand-line, window change fixes, Symmetry port
       Martin Boyer, Institut de recherche d’Hydro-Quebec, 1991
         autolist beeping options, modified the history search to  search  for
         the whole string from the beginning of the line to the cursor.
       Scott Krotz, Motorola, 1991
         Minix port
       David Dawes, Sydney U. Australia, Physics Dept., 1991
         SVR4 job control fixes
       Jose Sousa, Interactive Systems Corp., 1991
         Extended vi fixes and vi delete command
       Marc Horowitz, MIT, 1991
         ANSIfication fixes, new exec hashing code, imake fixes, where
       Bruce Sterling Woodcock, sterling@netcom.com, 1991-1995
         ETA  and Pyramid port, Makefile and lint fixes, ignoreeof=n addition,
         and various other portability changes and bug fixes
       Jeff Fink, 1992
         complete-word-fwd and complete-word-back
       Harry C. Pulley, 1992
         Coherent port
       Andy Phillips, Mullard Space Science Lab U.K., 1992
         VMS-POSIX port
       Beto Appleton, IBM Corp., 1992
         Walking process group fixes, csh bug fixes, POSIX file  tests,  POSIX
         SIGHUP
       Scott Bolte, Cray Computer Corp., 1992
         CSOS port
       Kaveh R. Ghazi, Rutgers University, 1992
         Tek,  m88k,  Titan  and  Masscomp  ports  and  fixes.  Added autoconf
         support.
       Mark Linderman, Cornell University, 1992
         OS/2 port
       Mika Liljeberg, liljeber@kruuna.Helsinki.FI, 1992
         Linux port
       Tim P. Starrin, NASA Langley Research Center Operations, 1993
         Read-only variables
       Dave Schweisguth, Yale University, 1993-4
         New man page and tcsh.man2html
       Larry Schwimmer, Stanford University, 1993
         AFS and HESIOD patches
       Luke Mewburn, RMIT University, 1994-6
         Enhanced directory printing in prompt, added ellipsis and rprompt.
       Edward Hutchins, Silicon Graphics Inc., 1996
         Added implicit cd.
       Martin Kraemer, 1997
         Ported to Siemens Nixdorf EBCDIC machine
       Amol Deshpande, Microsoft, 1997
         Ported to WIN32 (Windows/95 and Windows/NT); wrote  all  the  missing
         library and message catalog code to interface to Windows.
       Taga Nayuta, 1998
         Color ls additions.

THANKS TO

       Bryan Dunlap, Clayton Elwell, Karl Kleinpaste, Bob Manson, Steve Romig,
       Diana Smetters, Bob Sutterfield, Mark Verber, Elizabeth Zwicky and  all
       the other people at Ohio State for suggestions and encouragement

       All  the people on the net, for putting up with, reporting bugs in, and
       suggesting new additions to each and every version

       Richard M. Alderson III, for writing the ‘T in tcsh’ section