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<ol class="chapter"><li class="chapter-item expanded "><a href="The-Z-Shell-Manual.html"><strong aria-hidden="true">1.</strong> The Z Shell Manual</a></li><li class="chapter-item expanded "><a href="Introduction.html"><strong aria-hidden="true">2.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="Roadmap.html"><strong aria-hidden="true">3.</strong> Roadmap</a></li><li class="chapter-item expanded "><a href="Invocation.html"><strong aria-hidden="true">4.</strong> Invocation</a></li><li class="chapter-item expanded "><a href="Files.html"><strong aria-hidden="true">5.</strong> Files</a></li><li class="chapter-item expanded "><a href="Shell-Grammar.html"><strong aria-hidden="true">6.</strong> Shell Grammar</a></li><li class="chapter-item expanded "><a href="Redirection.html"><strong aria-hidden="true">7.</strong> Redirection</a></li><li class="chapter-item expanded "><a href="Command-Execution.html"><strong aria-hidden="true">8.</strong> Command Execution</a></li><li class="chapter-item expanded "><a href="Functions.html"><strong aria-hidden="true">9.</strong> Functions</a></li><li class="chapter-item expanded "><a href="Jobs-_0026-Signals.html"><strong aria-hidden="true">10.</strong> Jobs & Signals</a></li><li class="chapter-item expanded "><a href="Arithmetic-Evaluation.html"><strong aria-hidden="true">11.</strong> Arithmetic Evaluation</a></li><li class="chapter-item expanded "><a href="Conditional-Expressions.html" class="active"><strong aria-hidden="true">12.</strong> Conditional Expressions</a></li><li class="chapter-item expanded "><a href="Prompt-Expansion.html"><strong aria-hidden="true">13.</strong> Prompt Expansion</a></li><li class="chapter-item expanded "><a href="Expansion.html"><strong aria-hidden="true">14.</strong> Expansion</a></li><li class="chapter-item expanded "><a href="Parameters.html"><strong aria-hidden="true">15.</strong> Parameters</a></li><li class="chapter-item expanded "><a href="Options.html"><strong aria-hidden="true">16.</strong> Options</a></li><li class="chapter-item expanded "><a href="Shell-Builtin-Commands.html"><strong aria-hidden="true">17.</strong> Shell Builtin Commands</a></li><li class="chapter-item expanded "><a href="Zsh-Line-Editor.html"><strong aria-hidden="true">18.</strong> Zsh Line Editor</a></li><li class="chapter-item expanded "><a href="Completion-Widgets.html"><strong aria-hidden="true">19.</strong> Completion Widgets</a></li><li class="chapter-item expanded "><a href="Completion-System.html"><strong aria-hidden="true">20.</strong> Completion System</a></li><li class="chapter-item expanded "><a href="Completion-Using-compctl.html"><strong aria-hidden="true">21.</strong> Completion Using compctl</a></li><li class="chapter-item expanded "><a href="Zsh-Modules.html"><strong aria-hidden="true">22.</strong> Zsh Modules</a></li><li class="chapter-item expanded "><a href="Calendar-Function-System.html"><strong aria-hidden="true">23.</strong> Calendar Function System</a></li><li class="chapter-item expanded "><a href="TCP-Function-System.html"><strong aria-hidden="true">24.</strong> TCP Function System</a></li><li class="chapter-item expanded "><a href="Zftp-Function-System.html"><strong aria-hidden="true">25.</strong> Zftp Function System</a></li><li class="chapter-item expanded "><a href="User-Contributions.html"><strong aria-hidden="true">26.</strong> User Contributions</a></li></ol>
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<p><strong>Table of Contents</strong> <em>generated with <a href="https://github.com/thlorenz/doctoc">DocToc</a></em></p>
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<ul>
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<li><a href="#12-conditional-expressions">12 Conditional Expressions</a></li>
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</ul>
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<p><span id="Conditional-Expressions"></span>
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<span id="Conditional-Expressions-1"></span></p>
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<h1 id="12-conditional-expressions"><a class="header" href="#12-conditional-expressions">12 Conditional Expressions</a></h1>
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<p><span id="index-conditional-expressions"></span>
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<span id="index-expressions_002c-conditional"></span></p>
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<p>A <em>conditional expression</em> is used with the <code>[[</code> compound command to
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test attributes of files and to compare strings. Each expression can be
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constructed from one or more of the following unary or binary
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expressions:</p>
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<ul>
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<li>
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<p><code>-a</code> <code>file</code><br />
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true if <code>file</code> exists.</p>
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</li>
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<li>
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<p><code>-b</code> <code>file</code><br />
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true if <code>file</code> exists and is a block special file.</p>
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</li>
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<li>
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<p><code>-c</code> <code>file</code><br />
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true if <code>file</code> exists and is a character special file.</p>
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</li>
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<li>
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<p><code>-d</code> <code>file</code><br />
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true if <code>file</code> exists and is a directory.</p>
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</li>
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<li>
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<p><code>-e</code> <code>file</code><br />
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true if <code>file</code> exists.</p>
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</li>
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<li>
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<p><code>-f</code> <code>file</code><br />
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true if <code>file</code> exists and is a regular file.</p>
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</li>
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<li>
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<p><code>-g</code> <code>file</code><br />
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true if <code>file</code> exists and has its setgid bit set.</p>
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</li>
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<li>
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<p><code>-h</code> <code>file</code><br />
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true if <code>file</code> exists and is a symbolic link.</p>
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</li>
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<li>
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<p><code>-k</code> <code>file</code><br />
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true if <code>file</code> exists and has its sticky bit set.</p>
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</li>
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<li>
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<p><code>-n</code> <code>string</code><br />
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true if length of <code>string</code> is non-zero.</p>
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</li>
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<li>
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<p><code>-o</code> <code>option</code><br />
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true if option named <code>option</code> is on. <code>option</code> may be a single
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character, in which case it is a single letter option name. (See
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<a href="Options.html#Specifying-Options">Specifying Options</a>.)</p>
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<p>When no option named <code>option</code> exists, and the <code>POSIX_BUILTINS</code>
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option hasn’t been set, return 3 with a warning. If that option is
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set, return 1 with no warning.</p>
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</li>
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<li>
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<p><code>-p</code> <code>file</code><br />
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true if <code>file</code> exists and is a FIFO special file (named pipe).</p>
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</li>
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<li>
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<p><code>-r</code> <code>file</code><br />
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true if <code>file</code> exists and is readable by current process.</p>
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</li>
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<li>
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<p><code>-s</code> <code>file</code><br />
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true if <code>file</code> exists and has size greater than zero.</p>
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</li>
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<li>
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<p><code>-t</code> <code>fd</code><br />
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true if file descriptor number <code>fd</code> is open and associated with a
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terminal device. (note: <code>fd</code> is not optional)</p>
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</li>
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<li>
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<p><code>-u</code> <code>file</code><br />
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true if <code>file</code> exists and has its setuid bit set.</p>
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</li>
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<li>
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<p><code>-v</code> <code>varname</code><br />
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true if shell variable <code>varname</code> is set.</p>
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</li>
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<li>
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<p><code>-w</code> <code>file</code><br />
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<code>-x</code> <code>file</code><br />
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<code>-z</code> <code>string</code><br />
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true if length of <code>string</code> is zero.</p>
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</li>
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<li>
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<p><code>-L</code> <code>file</code><br />
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true if <code>file</code> exists and is a symbolic link.</p>
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</li>
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<li>
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<p><code>-O</code> <code>file</code><br />
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true if <code>file</code> exists and is owned by the effective user ID of this
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process.</p>
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</li>
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<li>
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<p><code>-G</code> <code>file</code><br />
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true if <code>file</code> exists and its group matches the effective group ID
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of this process.</p>
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</li>
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<li>
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<p><code>-S</code> <code>file</code><br />
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true if <code>file</code> exists and is a socket.</p>
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</li>
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<li>
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<p><code>-N</code> <code>file</code><br />
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true if <code>file</code> exists and its access time is not newer than its
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modification time.</p>
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</li>
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<li>
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<p><code>file1</code> <code>-nt</code> <code>file2</code><br />
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true if <code>file1</code> exists and is newer than <code>file2</code>.</p>
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</li>
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<li>
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<p><code>file1</code> <code>-ot</code> <code>file2</code><br />
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true if <code>file1</code> exists and is older than <code>file2</code>.</p>
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</li>
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<li>
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<p><code>file1</code> <code>-ef</code> <code>file2</code><br />
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true if <code>file1</code> and <code>file2</code> exist and refer to the same file.</p>
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</li>
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<li>
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<p><code>string</code> <code>=</code> <code>pattern</code><br />
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<code>string</code> <code>==</code> <code>pattern</code><br />
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true if <code>string</code> matches <code>pattern</code>. The two forms are exactly
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equivalent. The ‘<code>=</code>’ form is the traditional shell syntax (and
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hence the only one generally used with the <code>test</code> and <code>[</code> builtins);
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the ‘<code>==</code>’ form provides compatibility with other sorts of computer
|
||
language.</p>
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</li>
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||
<li>
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<p><code>string</code> <code>!=</code> <code>pattern</code><br />
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true if <code>string</code> does not match <code>pattern</code>.</p>
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||
</li>
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||
<li>
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<p><code>string</code> <code>=~</code> <code>regexp</code><br />
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true if <code>string</code> matches the regular expression <code>regexp</code>. If the
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||
option <code>RE_MATCH_PCRE</code> is set <code>regexp</code> is tested as a PCRE regular
|
||
expression using the <code>zsh/pcre</code> module, else it is tested as a POSIX
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||
extended regular expression using the <code>zsh/regex</code> module. Upon
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||
successful match, some variables will be updated; no variables are
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changed if the matching fails.</p>
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<p>If the option <code>BASH_REMATCH</code> is not set the scalar parameter <code>MATCH</code>
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is set to the substring that matched the pattern and the integer
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parameters <code>MBEGIN</code> and <code>MEND</code> to the index of the start and end,
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||
respectively, of the match in <code>string</code>, such that if <code>string</code> is
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contained in variable <code>var</code> the expression ‘<code>${var[$MBEGIN,$MEND]}</code>’
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is identical to ‘<code>$MATCH</code>’. The setting of the option <code>KSH_ARRAYS</code>
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is respected. Likewise, the array <code>match</code> is set to the substrings
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that matched parenthesised subexpressions and the arrays <code>mbegin</code>
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and <code>mend</code> to the indices of the start and end positions,
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respectively, of the substrings within <code>string</code>. The arrays are not
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set if there were no parenthesised subexpressions. For example, if
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the string ‘<code>a short string</code>’ is matched against the regular
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||
expression ‘<code>s(...)t</code>’, then (assuming the option <code>KSH_ARRAYS</code> is
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||
not set) <code>MATCH</code>, <code>MBEGIN</code> and <code>MEND</code> are ‘<code>short</code>’, <code>3</code> and <code>7</code>,
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respectively, while <code>match</code>, <code>mbegin</code> and <code>mend</code> are single entry
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arrays containing the strings ‘<code>hor</code>’, ‘<code>4</code>’ and ‘<code>6</code>’,
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||
respectively.</p>
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<p>If the option <code>BASH_REMATCH</code> is set the array <code>BASH_REMATCH</code> is set
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to the substring that matched the pattern followed by the substrings
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that matched parenthesised subexpressions within the pattern.</p>
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</li>
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<li>
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<p><code>string1</code> <code><</code> <code>string2</code><br />
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true if <code>string1</code> comes before <code>string2</code> based on ASCII value of
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their characters.</p>
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</li>
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<li>
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<p><code>string1</code> <code>></code> <code>string2</code><br />
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true if <code>string1</code> comes after <code>string2</code> based on ASCII value of
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their characters.</p>
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</li>
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<li>
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<p><code>exp1</code> <code>-eq</code> <code>exp2</code><br />
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true if <code>exp1</code> is numerically equal to <code>exp2</code>. Note that for purely
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numeric comparisons use of the <code>((``...``))</code> builtin described in
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||
<a href="Arithmetic-Evaluation.html#Arithmetic-Evaluation">Arithmetic
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||
Evaluation</a> is
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more convenient than conditional expressions.</p>
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</li>
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<li>
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<p><code>exp1</code> <code>-ne</code> <code>exp2</code><br />
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true if <code>exp1</code> is numerically not equal to <code>exp2</code>.</p>
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</li>
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<li>
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<p><code>exp1</code> <code>-lt</code> <code>exp2</code><br />
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true if <code>exp1</code> is numerically less than <code>exp2</code>.</p>
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</li>
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<li>
|
||
<p><code>exp1</code> <code>-gt</code> <code>exp2</code><br />
|
||
true if <code>exp1</code> is numerically greater than <code>exp2</code>.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>exp1</code> <code>-le</code> <code>exp2</code><br />
|
||
true if <code>exp1</code> is numerically less than or equal to <code>exp2</code>.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>exp1</code> <code>-ge</code> <code>exp2</code><br />
|
||
true if <code>exp1</code> is numerically greater than or equal to <code>exp2</code>.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>(</code> <code>exp</code> <code>)</code><br />
|
||
true if <code>exp</code> is true.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>!</code> <code>exp</code><br />
|
||
true if <code>exp</code> is false.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>exp1</code> <code>&&</code> <code>exp2</code><br />
|
||
true if <code>exp1</code> and <code>exp2</code> are both true.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>exp1</code> <code>||</code> <code>exp2</code><br />
|
||
true if either <code>exp1</code> or <code>exp2</code> is true.</p>
|
||
</li>
|
||
</ul>
|
||
<p>For compatibility, if there is a single argument that is not
|
||
syntactically significant, typically a variable, the condition is
|
||
treated as a test for whether the expression expands as a string of
|
||
non-zero length. In other words, <code>[[ $var ]]</code> is the same as <code>[[ -n $var ]]</code>. It is recommended that the second, explicit, form be used where
|
||
possible.</p>
|
||
<p>Normal shell expansion is performed on the <code>file</code>, <code>string</code> and
|
||
<code>pattern</code> arguments, but the result of each expansion is constrained to
|
||
be a single word, similar to the effect of double quotes.</p>
|
||
<p>Filename generation is not performed on any form of argument to
|
||
conditions. However, it can be forced in any case where normal shell
|
||
expansion is valid and when the option <code>EXTENDED_GLOB</code> is in effect by
|
||
using an explicit glob qualifier of the form <code>(#q)</code> at the end of the
|
||
string. A normal glob qualifier expression may appear between the ‘<code>q</code>’
|
||
and the closing parenthesis; if none appears the expression has no
|
||
effect beyond causing filename generation. The results of filename
|
||
generation are joined together to form a single word, as with the
|
||
results of other forms of expansion.</p>
|
||
<p>This special use of filename generation is only available with the <code>[[</code>
|
||
syntax. If the condition occurs within the <code>[</code> or <code>test</code> builtin
|
||
commands then globbing occurs instead as part of normal command line
|
||
expansion before the condition is evaluated. In this case it may
|
||
generate multiple words which are likely to confuse the syntax of the
|
||
test command.</p>
|
||
<p>For example,</p>
|
||
<div class="example">
|
||
<pre><code class="language-example">[[ -n file*(#qN) ]]
|
||
</code></pre>
|
||
</div>
|
||
<p>produces status zero if and only if there is at least one file in the
|
||
current directory beginning with the string ‘<code>file</code>’. The globbing
|
||
qualifier <code>N</code> ensures that the expression is empty if there is no
|
||
matching file.</p>
|
||
<p>Pattern metacharacters are active for the <code>pattern</code> arguments; the
|
||
patterns are the same as those used for filename generation, see
|
||
<a href="Expansion.html#Filename-Generation">Filename Generation</a>, but there is
|
||
no special behaviour of ‘<code>/</code>’ nor initial dots, and no glob qualifiers
|
||
are allowed.</p>
|
||
<p>In each of the above expressions, if <code>file</code> is of the form
|
||
‘<code>/dev/fd/``n</code>’, where <code>n</code> is an integer, then the test applied to the
|
||
open file whose descriptor number is <code>n</code>, even if the underlying system
|
||
does not support the <code>/dev/fd</code> directory.</p>
|
||
<p>In the forms which do numeric comparison, the expressions <code>exp</code> undergo
|
||
arithmetic expansion as if they were enclosed in <code>$((``...``))</code>.</p>
|
||
<p>For example, the following:</p>
|
||
<div class="example">
|
||
<pre><code class="language-example">[[ ( -f foo || -f bar ) && $report = y* ]] && print File exists.
|
||
</code></pre>
|
||
</div>
|
||
<p>tests if either file <code>foo</code> or file <code>bar</code> exists, and if so, if the value
|
||
of the parameter <code>report</code> begins with ‘<code>y</code>’; if the complete condition
|
||
is true, the message ‘<code>File exists.</code>’ is printed.</p>
|
||
<hr />
|
||
<p>This document was generated on <em>February 15, 2020</em> using
|
||
<a href="http://www.nongnu.org/texi2html/"><em>texi2html 5.0</em></a>.<br />
|
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Zsh version 5.8, released on February 14, 2020.</p>
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