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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.