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<div class="refnamediv">
<h1 class="refname">exec</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">exec</span> — <span class="dc-title">Execute an external program</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.exec-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">string</span> <span class="methodname"><strong>exec</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$command</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter reference">&$output</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter reference">&$return_var</code></span>
]] )</div>
<p class="para rdfs-comment">
<span class="function"><strong>exec()</strong></span> executes the given
<em><code class="parameter">command</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.exec-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">command</code></em></span>
<dd>
<p class="para">
The command that will be executed.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">output</code></em></span>
<dd>
<p class="para">
If the <em><code class="parameter">output</code></em> argument is present, then the
specified array will be filled with every line of output from the
command. Trailing whitespace, such as <em>\n</em>, is not
included in this array. Note that if the array already contains some
elements, <span class="function"><strong>exec()</strong></span> will append to the end of the array.
If you do not want the function to append elements, call
<span class="function"><a href="function.unset.html" class="function">unset()</a></span> on the array before passing it to
<span class="function"><strong>exec()</strong></span>.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">return_var</code></em></span>
<dd>
<p class="para">
If the <em><code class="parameter">return_var</code></em> argument is present
along with the <em><code class="parameter">output</code></em> argument, then the
return status of the executed command will be written to this
variable.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.exec-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
The last line from the result of the command. If you need to execute a
command and have all the data from the command passed directly back without
any interference, use the <span class="function"><a href="function.passthru.html" class="function">passthru()</a></span> function.
</p>
<p class="para">
To get the output of the executed command, be sure to set and use the
<em><code class="parameter">output</code></em> parameter.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.exec-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-3676">
<p><strong>Example #1 An <span class="function"><strong>exec()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// outputs the username that owns the running php/httpd process<br />// (on a system with the "whoami" executable in the path)<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">exec</span><span style="color: #007700">(</span><span style="color: #DD0000">'whoami'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.exec-notes">
<h3 class="title">Notes</h3>
<div class="warning"><strong class="warning">Warning</strong><p class="para">When allowing user-supplied data to be
passed to this function, use
<span class="function"><a href="function.escapeshellarg.html" class="function">escapeshellarg()</a></span> or <span class="function"><a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a></span>
to ensure that users cannot trick the system into executing arbitrary
commands.</p></div>
<blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">If a program is started with this function,
in order for it to continue running in the background, the output of the
program must be redirected to a file or another output stream. Failing to do so
will cause PHP to hang until the execution of the program ends.</p></p></blockquote>
<blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">When
<a href="features.safe-mode.html" class="link">safe mode</a> is enabled, you can only
execute files within the <a href="ini.sect.safe-mode.html#ini.safe-mode-exec-dir" class="link">safe_mode_exec_dir</a>.
For practical reasons, it is currently not allowed to have <em>..</em>
components in the path to the executable.</span></p></blockquote>
<div class="warning"><strong class="warning">Warning</strong><p class="simpara">With <a href="features.safe-mode.html" class="link">safe mode</a> enabled,
the command string is escaped with <span class="function"><a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a></span>. Thus,
<em>echo y | echo x</em> becomes <em>echo y \| echo x</em>.</p></div>
</div>
<div class="refsect1 seealso" id="refsect1-function.exec-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.system.html" class="function" rel="rdfs-seeAlso">system()</a> - Execute an external program and display the output</span></li>
<li class="member"> <span class="function"><a href="function.passthru.html" class="function" rel="rdfs-seeAlso">passthru()</a> - Execute an external program and display raw output</span></li>
<li class="member"> <span class="function"><a href="function.escapeshellcmd.html" class="function" rel="rdfs-seeAlso">escapeshellcmd()</a> - Escape shell metacharacters</span></li>
<li class="member"> <span class="function"><a href="function.pcntl-exec.html" class="function" rel="rdfs-seeAlso">pcntl_exec()</a> - Executes specified program in current process space</span></li>
<li class="member"><a href="language.operators.execution.html" class="link">backtick operator</a></li>
</ul>
</p>
</div>
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