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<a name="Invocation"></a>
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<a name="Invocation-1"></a>
<h1 class="chapter">4 Invocation</h1>
<p><a name="index-invocation"></a>
</p>
<hr>
<a name="Invocation-2"></a>
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<h2 class="section">4.1 Invocation</h2>
<p><a name="index-shell-options"></a>
<a name="index-options_002c-shell"></a>
<a name="index-shell-flags"></a>
<a name="index-flags_002c-shell"></a>
The following flags are interpreted by the shell when invoked to determine
where the shell will read commands from:
</p>
<dl compact="compact">
<dt><tt>-c</tt></dt>
<dd><p>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 <tt>$0</tt>, rather than being used as a positional
parameter.
</p>
</dd>
<dt><tt>-i</tt></dt>
<dd><p>Force shell to be interactive. It is still possible to specify a
script to execute.
</p>
</dd>
<dt><tt>-s</tt></dt>
<dd><p>Force shell to read commands from the standard input.
If the <tt>-s</tt> flag is not present and an argument is given,
the first argument is taken to be the pathname of a script to
execute.
</p>
</dd>
</dl>
<p>If there are any remaining arguments after option processing, and neither
of the options <tt>-c</tt> or <tt>-s</tt> was supplied, the first argument is taken
as the file name of a script containing shell commands to be executed. If
the option <tt>PATH_SCRIPT</tt> is set, and the file name does not contain a
directory path (i.e. there is no ‘<tt>/</tt>’ in the name), first the current
directory and then the command path given by the variable <tt>PATH</tt> are
searched for the script. If the option is not set or the file name
contains a ‘<tt>/</tt>’ it is used directly.
</p>
<p>After the first one or two arguments have been appropriated as described above,
the remaining arguments are assigned to the positional parameters.
</p>
<p>For further options, which are common to invocation and the <tt>set</tt>
builtin, see
<a href="Options.html#Options">Options</a>.
</p>
<p>Options may be specified by name using the <tt>-o</tt> option. <tt>-o</tt> acts like
a single-letter option, but takes a following string as the option name.
For example,
</p>
<div class="example">
<pre class="example">zsh -x -o shwordsplit scr
</pre></div>
<p>runs the script <tt>scr</tt>, setting the <tt>XTRACE</tt> option by the corresponding
letter ‘<tt>-x</tt>’ and the <tt>SH_WORD_SPLIT</tt> option by name.
Options may be turned <em>off</em> by name by using <tt>+o</tt> instead of <tt>-o</tt>.
<tt>-o</tt> can be stacked up with preceding single-letter options, so for example
‘<tt>-xo shwordsplit</tt>’ or ‘<tt>-xoshwordsplit</tt>’ is equivalent to
‘<tt>-x -o shwordsplit</tt>’.
</p>
<p><a name="index-long-option"></a>
Options may also be specified by name in GNU long option style,
‘<tt>-</tt><tt>-</tt><var>option-name</var>’. When this is done, ‘<tt>-</tt>’ characters in the
option name are permitted: they are translated into ‘<tt>_</tt>’, and thus ignored.
So, for example, ‘<tt>zsh -</tt><tt>-sh-word-split</tt>’ invokes zsh with the
<tt>SH_WORD_SPLIT</tt> option turned on. Like other option syntaxes, options can
be turned off by replacing the initial ‘<tt>-</tt>’ with a ‘<tt>+</tt>’; thus
‘<tt>+-sh-word-split</tt>’ is equivalent to ‘<tt>-</tt><tt>-no-sh-word-split</tt>’.
Unlike other option syntaxes, GNU-style long options cannot be stacked with
any other options, so for example ‘<tt>-x-shwordsplit</tt>’ is an error,
rather than being treated like ‘<tt>-x -</tt><tt>-shwordsplit</tt>’.
</p>
<p><a name="index-_002d_002dversion"></a>
<a name="index-_002d_002dhelp"></a>
The special GNU-style option ‘<tt>-</tt><tt>-version</tt>’ is handled; it sends to
standard output the shell’s version information, then exits successfully.
‘<tt>-</tt><tt>-help</tt>’ is also handled; it sends to standard output a list of
options that can be used when invoking the shell, then exits successfully.
</p>
<p>Option processing may be finished, allowing following arguments that start with
‘<tt>-</tt>’ or ‘<tt>+</tt>’ to be treated as normal arguments, in two ways.
Firstly, a lone ‘<tt>-</tt>’ (or ‘<tt>+</tt>’) as an argument by itself ends
option processing. Secondly, a special option ‘<tt>-</tt><tt>-</tt>’ (or
‘<tt>+-</tt>’), which may be specified on its own (which is the standard
POSIX usage) or may be stacked with preceding options (so ‘<tt>-x-</tt>’ is
equivalent to ‘<tt>-x -</tt><tt>-</tt>’). Options are not permitted to be stacked
after ‘<tt>-</tt><tt>-</tt>’ (so ‘<tt>-x-f</tt>’ is an error), but note the GNU-style
option form discussed above, where ‘<tt>-</tt><tt>-shwordsplit</tt>’ is permitted
and does not end option processing.
</p>
<p>Except when the <cite>sh</cite>/<cite>ksh</cite> emulation single-letter options are in effect,
the option ‘<tt>-b</tt>’ (or ‘<tt>+b</tt>’) ends option processing.
‘<tt>-b</tt>’ is like ‘<tt>-</tt><tt>-</tt>’, except that further single-letter options
can be stacked after the ‘<tt>-b</tt>’ and will take effect as normal.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Compatibility">4.2 Compatibility</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#Restricted-Shell">4.3 Restricted Shell</a></td><td> </td><td align="left" valign="top">
</td></tr>
</table>
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<a name="Compatibility-1"></a>
<h2 class="section">4.2 Compatibility</h2>
<p><a name="index-compatibility"></a>
<a name="index-sh-compatibility"></a>
<a name="index-ksh-compatibility"></a>
Zsh tries to emulate <cite>sh</cite> or <cite>ksh</cite> when it is invoked as
<tt>sh</tt> or <tt>ksh</tt> respectively; more precisely, it looks at the first
letter of the name by which it was invoked, excluding any initial ‘<tt>r</tt>’
(assumed to stand for ‘restricted’), and if that is ‘<tt>b</tt>’, ‘<tt>s</tt>’ or ‘<tt>k</tt>’ it
will emulate <cite>sh</cite> or <cite>ksh</cite>. Furthermore, if invoked as <tt>su</tt> (which
happens on certain systems when the shell is executed by the <tt>su</tt>
command), the shell will try to find an alternative name from the <tt>SHELL</tt>
environment variable and perform emulation based on that.
</p>
<p>In <cite>sh</cite> and <cite>ksh</cite> compatibility modes the following
parameters are not special and not initialized by the shell:
<tt>ARGC</tt>,
<tt>argv</tt>,
<tt>cdpath</tt>,
<tt>fignore</tt>,
<tt>fpath</tt>,
<tt>HISTCHARS</tt>,
<tt>mailpath</tt>,
<tt>MANPATH</tt>,
<tt>manpath</tt>,
<tt>path</tt>,
<tt>prompt</tt>,
<tt>PROMPT</tt>,
<tt>PROMPT2</tt>,
<tt>PROMPT3</tt>,
<tt>PROMPT4</tt>,
<tt>psvar</tt>,
<tt>status</tt>,
<tt>watch</tt>.
</p>
<p><a name="index-ENV_002c-use-of"></a>
The usual zsh startup/shutdown scripts are not executed. Login shells
source <tt>/etc/profile</tt> followed by <tt>$HOME/.profile</tt>. If the
<tt>ENV</tt> environment variable is set on invocation, <tt>$ENV</tt> is sourced
after the profile scripts. The value of <tt>ENV</tt> is subjected to
parameter expansion, command substitution, and arithmetic expansion
before being interpreted as a pathname. Note that the <tt>PRIVILEGED</tt>
option also affects the execution of startup files.
</p>
<p>The following options are set if the shell is invoked as <tt>sh</tt> or
<tt>ksh</tt>:
<tt>NO_BAD_PATTERN</tt>,
<tt>NO_BANG_HIST</tt>,
<tt>NO_BG_NICE</tt>,
<tt>NO_EQUALS</tt>,
<tt>NO_FUNCTION_ARGZERO</tt>,
<tt>GLOB_SUBST</tt>,
<tt>NO_GLOBAL_EXPORT</tt>,
<tt>NO_HUP</tt>,
<tt>INTERACTIVE_COMMENTS</tt>,
<tt>KSH_ARRAYS</tt>,
<tt>NO_MULTIOS</tt>,
<tt>NO_NOMATCH</tt>,
<tt>NO_NOTIFY</tt>,
<tt>POSIX_BUILTINS</tt>,
<tt>NO_PROMPT_PERCENT</tt>,
<tt>RM_STAR_SILENT</tt>,
<tt>SH_FILE_EXPANSION</tt>,
<tt>SH_GLOB</tt>,
<tt>SH_OPTION_LETTERS</tt>,
<tt>SH_WORD_SPLIT</tt>.
Additionally the <tt>BSD_ECHO</tt> and <tt>IGNORE_BRACES</tt>
options are set if zsh is invoked as <tt>sh</tt>.
Also, the
<tt>KSH_OPTION_PRINT</tt>,
<tt>LOCAL_OPTIONS</tt>,
<tt>PROMPT_BANG</tt>,
<tt>PROMPT_SUBST</tt>
and
<tt>SINGLE_LINE_ZLE</tt>
options are set if zsh is invoked as <tt>ksh</tt>.
</p><hr>
<a name="Restricted-Shell"></a>
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<a name="Restricted-Shell-1"></a>
<h2 class="section">4.3 Restricted Shell</h2>
<p><a name="index-restricted-shell"></a>
<a name="index-RESTRICTED"></a>
When the basename of the command used to invoke zsh starts with the letter
‘<tt>r</tt>’ or the ‘<tt>-r</tt>’ command line option is supplied at invocation, the
shell becomes restricted. Emulation mode is determined after stripping the
letter ‘<tt>r</tt>’ from the invocation name. The following are disabled in
restricted mode:
</p>
<ul>
<li> changing directories with the <tt>cd</tt> builtin
</li><li> changing or unsetting the <tt>EGID</tt>, <tt>EUID</tt>, <tt>GID</tt>,
<tt>HISTFILE</tt>, <tt>HISTSIZE</tt>, <tt>IFS</tt>, <tt>LD_AOUT_LIBRARY_PATH</tt>,
<tt>LD_AOUT_PRELOAD</tt>, <tt>LD_LIBRARY_PATH</tt>, <tt>LD_PRELOAD</tt>,
<tt>MODULE_PATH</tt>, <tt>module_path</tt>, <tt>PATH</tt>, <tt>path</tt>, <tt>SHELL</tt>,
<tt>UID</tt> and <tt>USERNAME</tt> parameters
</li><li> specifying command names containing <tt>/</tt>
</li><li> specifying command pathnames using <tt>hash</tt>
</li><li> redirecting output to files
</li><li> using the <tt>exec</tt> builtin command to replace the shell with another
command
</li><li> using <tt>jobs -Z</tt> to overwrite the shell process’ argument and
environment space
</li><li> using the <tt>ARGV0</tt> parameter to override <tt>argv[0]</tt> for external
commands
</li><li> turning off restricted mode with <tt>set +r</tt> or <tt>unsetopt
RESTRICTED</tt>
</li></ul>
<p>These restrictions are enforced after processing the startup files. The
startup files should set up <tt>PATH</tt> 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.
</p>
<p>Restricted mode can also be activated any time by setting the
<tt>RESTRICTED</tt> option. This immediately enables all the restrictions
described above even if the shell still has not processed all startup
files.
</p><hr>
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<p><font size="-1">
This document was generated on <em>April 11, 2017</em> using <a href="http://www.gnu.org/software/texinfo/"><em>texi2any</em></a>.
</font></p>
<font size="-1">Zsh version 5.3.1, released on December 21, 2016.</font>
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