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NAME

       zsh - the Z shell

OVERVIEW

       Because  zsh  contains  many  features,  the  zsh  manual  has been split into a number of
       sections:

       zsh          Zsh overview (this section)
       zshroadmap   Informal introduction to the manual
       zshmisc      Anything not fitting into the other sections
       zshexpn      Zsh command and parameter expansion
       zshparam     Zsh parameters
       zshoptions   Zsh options
       zshbuiltins  Zsh built-in functions
       zshzle       Zsh command line editing
       zshcompwid   Zsh completion widgets
       zshcompsys   Zsh completion system
       zshcompctl   Zsh completion control
       zshmodules   Zsh loadable modules
       zshcalsys    Zsh built-in calendar functions
       zshtcpsys    Zsh built-in TCP functions
       zshzftpsys   Zsh built-in FTP client
       zshcontrib   Additional zsh functions and utilities
       zshall       Meta-man page containing all of the above

DESCRIPTION

       Zsh is a UNIX command interpreter (shell) usable as an interactive login shell  and  as  a
       shell  script  command  processor.  Of the standard shells, zsh most closely resembles ksh
       but includes many enhancements.  It does not provide compatibility  with  POSIX  or  other
       shells in its default operating mode:  see the section Compatibility below.

       Zsh   has   command  line  editing,  builtin  spelling  correction,  programmable  command
       completion, shell functions (with autoloading), a history mechanism, and a host  of  other
       features.

AUTHOR

       Zsh  was  originally  written  by Paul Falstad <pf@zsh.org>.  Zsh is now maintained by the
       members of  the  zsh-workers  mailing  list  <zsh-workers@zsh.org>.   The  development  is
       currently coordinated by Peter Stephenson <pws@zsh.org>.  The coordinator can be contacted
       at <coordinator@zsh.org>, but matters relating to the code  should  generally  go  to  the
       mailing list.

AVAILABILITY

       Zsh is available from the following HTTP and anonymous FTP site.

       ftp://ftp.zsh.org/pub/
       https://www.zsh.org/pub/
       )

       The   up-to-date   source   code   is   available   via   Git   from   Sourceforge.    See
       https://sourceforge.net/projects/zsh/ for details.  A  summary  of  instructions  for  the
       archive can be found at http://zsh.sourceforge.net/.

MAILING LISTS

       Zsh has 3 mailing lists:

       <zsh-announce@zsh.org>
              Announcements about releases, major changes in the shell and the monthly posting of
              the Zsh FAQ.  (moderated)

       <zsh-users@zsh.org>
              User discussions.

       <zsh-workers@zsh.org>
              Hacking, development, bug reports and patches.

       To subscribe or unsubscribe, send mail to the associated administrative  address  for  the
       mailing list.

       <zsh-announce-subscribe@zsh.org>
       <zsh-users-subscribe@zsh.org>
       <zsh-workers-subscribe@zsh.org>
       <zsh-announce-unsubscribe@zsh.org>
       <zsh-users-unsubscribe@zsh.org>
       <zsh-workers-unsubscribe@zsh.org>

       YOU  ONLY  NEED  TO  JOIN ONE OF THE MAILING LISTS AS THEY ARE NESTED.  All submissions to
       zsh-announce are automatically forwarded to zsh-users.  All submissions to  zsh-users  are
       automatically forwarded to zsh-workers.

       If  you  have problems subscribing/unsubscribing to any of the mailing lists, send mail to
       <listmaster@zsh.org>.   The   mailing   lists   are   maintained   by   Karsten   Thygesen
       <karthy@kom.auc.dk>.

       The  mailing  lists  are  archived;  the  archives  can be accessed via the administrative
       addresses listed above.  There is also a  hypertext  archive,  maintained  by  Geoff  Wing
       <gcw@zsh.org>, available at https://www.zsh.org/mla/.

THE ZSH FAQ

       Zsh  has  a  list  of  Frequently  Asked  Questions  (FAQ), maintained by Peter Stephenson
       <pws@zsh.org>.   It  is  regularly  posted  to  the  newsgroup  comp.unix.shell  and   the
       zsh-announce  mailing  list.  The latest version can be found at any of the Zsh FTP sites,
       or  at  http://www.zsh.org/FAQ/.   The  contact  address  for   FAQ-related   matters   is
       <faqmaster@zsh.org>.

THE ZSH WEB PAGE

       Zsh  has  a  web  page  which  is  located at https://www.zsh.org/.  This is maintained by
       Karsten  Thygesen  <karthy@zsh.org>,  of  SunSITE  Denmark.   The  contact   address   for
       web-related matters is <webmaster@zsh.org>.

THE ZSH USERGUIDE

       A  userguide  is  currently in preparation.  It is intended to complement the manual, with
       explanations and hints on issues where the manual can  be  cabbalistic,  hierographic,  or
       downright  mystifying  (for  example,  the word `hierographic' does not exist).  It can be
       viewed in its current state at http://zsh.sourceforge.net/Guide/.  At the time of writing,
       chapters  dealing with startup files and their contents and the new completion system were
       essentially complete.

INVOCATION

       The following flags are interpreted by the shell when invoked to determine where the shell
       will read commands from:

       -c     Take  the first argument as a command to execute, rather than reading commands from
              a script or standard input.  If any further arguments are given, the first  one  is
              assigned to $0, rather than being used as a positional parameter.

       -i     Force  shell  to  be  interactive.   It  is  still  possible to specify a script to
              execute.

       -s     Force shell to read commands from the standard  input.   If  the  -s  flag  is  not
              present and an argument is given, the first argument is taken to be the pathname of
              a script to execute.

       If there are any remaining arguments after option processing, and neither of  the  options
       -c or -s was supplied, the first argument is taken as the file name of a script containing
       shell commands to be executed.  If the option PATH_SCRIPT is set, and the file  name  does
       not  contain  a  directory  path  (i.e.  there  is  no `/' in the name), first the current
       directory and then the command path given by  the  variable  PATH  are  searched  for  the
       script.  If the option is not set or the file name contains a `/' it is used directly.

       After  the  first  one  or  two  arguments  have been appropriated as described above, the
       remaining arguments are assigned to the positional parameters.

       For  further  options,  which  are  common  to  invocation  and  the  set   builtin,   see
       zshoptions(1).

       The  long  option  `--emulate'  followed  (in a separate word) by an emulation mode may be
       passed to the shell.  The emulation modes are those described for the emulate builtin, see
       zshbuiltins(1).   The  `--emulate'  option  must  precede  any  other options (which might
       otherwise be overridden), but following options are honoured, so may be used to modify the
       requested  emulation  mode.   Note  that  certain extra steps are taken to ensure a smooth
       emulation when this option is used compared with the emulate command within the shell: for
       example,  variables that conflict with POSIX usage such as path are not defined within the
       shell.

       Options may be specified by name using the  -o  option.   -o  acts  like  a  single-letter
       option, but takes a following string as the option name.  For example,

              zsh -x -o shwordsplit scr

       runs  the  script  scr, setting the XTRACE option by the corresponding letter `-x' and the
       SH_WORD_SPLIT option by name.  Options may be turned off by name by using  +o  instead  of
       -o.   -o  can  be  stacked  up  with  preceding single-letter options, so for example `-xo
       shwordsplit' or `-xoshwordsplit' is equivalent to `-x -o shwordsplit'.

       Options may also be specified by name in GNU long  option  style,  `--option-name'.   When
       this  is  done,  `-' characters in the option name are permitted: they are translated into
       `_', and thus ignored.  So, for  example,  `zsh  --sh-word-split'  invokes  zsh  with  the
       SH_WORD_SPLIT  option turned on.  Like other option syntaxes, options can be turned off by
       replacing  the  initial  `-'  with  a  `+';  thus  `+-sh-word-split'  is   equivalent   to
       `--no-sh-word-split'.   Unlike  other  option  syntaxes,  GNU-style long options cannot be
       stacked with any other options, so for example `-x-shwordsplit' is an error,  rather  than
       being treated like `-x --shwordsplit'.

       The  special  GNU-style  option  `--version'  is  handled; it sends to standard output the
       shell's version information, then exits successfully.  `--help' is also handled; it  sends
       to  standard output a list of options that can be used when invoking the shell, then exits
       successfully.

       Option processing may be finished, allowing following arguments that start with `-' or `+'
       to  be  treated  as  normal  arguments,  in  two ways.  Firstly, a lone `-' (or `+') as an
       argument by itself ends option processing.  Secondly, a special  option  `--'  (or  `+-'),
       which  may  be  specified on its own (which is the standard POSIX usage) or may be stacked
       with preceding options (so `-x-' is equivalent to `-x --').  Options are not permitted  to
       be  stacked  after  `--'  (so  `-x-f'  is  an  error),  but note the GNU-style option form
       discussed above, where `--shwordsplit' is permitted and does not end option processing.

       Except when the sh/ksh emulation single-letter options are in effect, the option `-b'  (or
       `+b')  ends  option  processing.   `-b'  is  like  `--', except that further single-letter
       options can be stacked after the `-b' and will take effect as normal.

COMPATIBILITY

       Zsh tries to emulate sh or ksh when  it  is  invoked  as  sh  or  ksh  respectively;  more
       precisely, it looks at the first letter of the name by which it was invoked, excluding any
       initial `r' (assumed to stand for `restricted'), and if that is `b', `s' or  `k'  it  will
       emulate  sh  or ksh.  Furthermore, if invoked as su (which happens on certain systems when
       the shell is executed by the su command), the shell will try to find an  alternative  name
       from the SHELL environment variable and perform emulation based on that.

       In  sh  and  ksh  compatibility  modes  the  following  parameters are not special and not
       initialized by the  shell:  ARGC,  argv,  cdpath,  fignore,  fpath,  HISTCHARS,  mailpath,
       MANPATH, manpath, path, prompt, PROMPT, PROMPT2, PROMPT3, PROMPT4, psvar, status, watch.

       The usual zsh startup/shutdown scripts are not executed.  Login shells source /etc/profile
       followed by $HOME/.profile.  If the ENV environment variable is set on invocation, $ENV is
       sourced  after the profile scripts.  The value of ENV is subjected to parameter expansion,
       command substitution, and arithmetic expansion before being  interpreted  as  a  pathname.
       Note that the PRIVILEGED option also affects the execution of startup files.

       The  following  options  are  set  if  the  shell is invoked as sh or ksh: NO_BAD_PATTERN,
       NO_BANG_HIST, NO_BG_NICE, NO_EQUALS,  NO_FUNCTION_ARGZERO,  GLOB_SUBST,  NO_GLOBAL_EXPORT,
       NO_HUP,    INTERACTIVE_COMMENTS,    KSH_ARRAYS,    NO_MULTIOS,    NO_NOMATCH,   NO_NOTIFY,
       POSIX_BUILTINS,    NO_PROMPT_PERCENT,    RM_STAR_SILENT,    SH_FILE_EXPANSION,    SH_GLOB,
       SH_OPTION_LETTERS, SH_WORD_SPLIT.  Additionally the BSD_ECHO and IGNORE_BRACES options are
       set if zsh is invoked as sh.   Also,  the  KSH_OPTION_PRINT,  LOCAL_OPTIONS,  PROMPT_BANG,
       PROMPT_SUBST and SINGLE_LINE_ZLE options are set if zsh is invoked as ksh.

RESTRICTED SHELL

       When the basename of the command used to invoke zsh starts with the letter `r' or the `-r'
       command line option is supplied at invocation, the shell  becomes  restricted.   Emulation
       mode is determined after stripping the letter `r' from the invocation name.  The following
       are disabled in restricted mode:

       ·      changing directories with the cd builtin

       ·      changing  or  unsetting   the   EGID,   EUID,   GID,   HISTFILE,   HISTSIZE,   IFS,
              LD_AOUT_LIBRARY_PATH,  LD_AOUT_PRELOAD,  LD_LIBRARY_PATH,  LD_PRELOAD, MODULE_PATH,
              module_path, PATH, path, SHELL, UID and USERNAME parameters

       ·      specifying command names containing /

       ·      specifying command pathnames using hash

       ·      redirecting output to files

       ·      using the exec builtin command to replace the shell with another command

       ·      using jobs -Z to overwrite the shell process' argument and environment space

       ·      using the ARGV0 parameter to override argv[0] for external commands

       ·      turning off restricted mode with set +r or unsetopt RESTRICTED

       These restrictions are enforced after processing the startup  files.   The  startup  files
       should  set up PATH to point to a directory of commands which can be safely invoked in the
       restricted environment.  They may also add  further  restrictions  by  disabling  selected
       builtins.

       Restricted  mode  can  also  be activated any time by setting the RESTRICTED option.  This
       immediately enables all the restrictions described above even if the shell still  has  not
       processed all startup files.

       A  shell Restricted Mode is an outdated way to restrict what users may do:  modern systems
       have better, safer and more reliable ways to confine user actions, such as  chroot  jails,
       containers and zones.

       A restricted shell is very difficult to implement safely.  The feature may be removed in a
       future version of zsh.

       It is important to realise that the restrictions only apply  to  the  shell,  not  to  the
       commands  it runs (except for some shell builtins).  While a restricted shell can only run
       the restricted list of commands accessible via the predefined `PATH' variable, it does not
       prevent those commands from running any other command.

       As  an example, if `env' is among the list of allowed commands, then it allows the user to
       run any command as `env' is not a shell builtin command and can run arbitrary executables.

       So when implementing a restricted shell framework it is important to  be  fully  aware  of
       what  actions  each of the allowed commands or features (which may be regarded as modules)
       can perform.

       Many commands can have their behaviour affected by environment variables.  Except for  the
       few listed above, zsh does not restrict the setting of environment variables.

       If a `perl', `python', `bash', or other general purpose interpreted script it treated as a
       restricted command, the user can work around the restriction by setting specially  crafted
       `PERL5LIB',  `PYTHONPATH',  `BASHENV'  (etc.)  environment  variables. On GNU systems, any
       command can be made to  run  arbitrary  code  when  performing  character  set  conversion
       (including  zsh  itself) by setting a `GCONV_PATH' environment variable.  Those are only a
       few examples.

       Bear in mind that, contrary to some other shells, `readonly' is not a security feature  in
       zsh as it can be undone and so cannot be used to mitigate the above.

       A  restricted shell only works if the allowed commands are few and carefully written so as
       not to grant more access to users than intended.  It is also important  to  restrict  what
       zsh  module  the  user  may  load as some of them, such as `zsh/system', `zsh/mapfile' and
       `zsh/files', allow bypassing most of the restrictions.

STARTUP/SHUTDOWN FILES

       Commands are first read from  /etc/zsh/zshenv;  this  cannot  be  overridden.   Subsequent
       behaviour  is  modified  by the RCS and GLOBAL_RCS options; the former affects all startup
       files, while the second only affects global startup files (those shown here with  an  path
       starting  with  a /).  If one of the options is unset at any point, any subsequent startup
       file(s) of the corresponding type will not be read.  It is also possible  for  a  file  in
       $ZDOTDIR to re-enable GLOBAL_RCS. Both RCS and GLOBAL_RCS are set by default.

       Commands are then read from $ZDOTDIR/.zshenv.  If the shell is a login shell, commands are
       read  from  /etc/zsh/zprofile  and  then  $ZDOTDIR/.zprofile.   Then,  if  the  shell   is
       interactive,  commands are read from /etc/zsh/zshrc and then $ZDOTDIR/.zshrc.  Finally, if
       the shell is a login shell, /etc/zsh/zlogin and $ZDOTDIR/.zlogin are read.

       When a login shell exits, the files $ZDOTDIR/.zlogout and then /etc/zsh/zlogout are  read.
       This  happens with either an explicit exit via the exit or logout commands, or an implicit
       exit by reading end-of-file from the terminal.  However, if the shell  terminates  due  to
       exec'ing  another  process, the logout files are not read.  These are also affected by the
       RCS and GLOBAL_RCS options.  Note also that the RCS option affects the saving  of  history
       files, i.e. if RCS is unset when the shell exits, no history file will be saved.

       If  ZDOTDIR is unset, HOME is used instead.  Files listed above as being in /etc may be in
       another directory, depending on the installation.

       As /etc/zsh/zshenv is run for all instances of zsh, it is important that  it  be  kept  as
       small  as possible.  In particular, it is a good idea to put code that does not need to be
       run for every single shell behind a test of the form `if [[ -o rcs ]]; then ...'  so  that
       it will not be executed when zsh is invoked with the `-f' option.

       Any   of  these  files  may  be  pre-compiled  with  the  zcompile  builtin  command  (see
       zshbuiltins(1)).  If a compiled file exists (named for the original  file  plus  the  .zwc
       extension) and it is newer than the original file, the compiled file will be used instead.

FILES

       $ZDOTDIR/.zshenv
       $ZDOTDIR/.zprofile
       $ZDOTDIR/.zshrc
       $ZDOTDIR/.zlogin
       $ZDOTDIR/.zlogout
       ${TMPPREFIX}*   (default is /tmp/zsh*)
       /etc/zsh/zshenv
       /etc/zsh/zprofile
       /etc/zsh/zshrc
       /etc/zsh/zlogin
       /etc/zsh/zlogout    (installation-specific - /etc is the default)

SEE ALSO

       sh(1),  csh(1),  tcsh(1), rc(1), bash(1), ksh(1), zshall(1), zshbuiltins(1), zshcalsys(1),
       zshcompwid(1),  zshcompsys(1),  zshcompctl(1),  zshcontrib(1),   zshexpn(1),   zshmisc(1),
       zshmodules(1),  zshoptions(1),  zshparam(1),  zshroadmap(1),  zshtcpsys(1), zshzftpsys(1),
       zshzle(1)

       IEEE Standard for information Technology - Portable Operating System Interface  (POSIX)  -
       Part 2: Shell and Utilities, IEEE Inc, 1993, ISBN 1-55937-255-9.