<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Execute an external program and display the output</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.shell-exec.html">shell_exec</a></div> <div class="next" style="text-align: right; float: right;"><a href="book.pthreads.html">pthreads</a></div> <div class="up"><a href="ref.exec.html">Program execution Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="function.system" class="refentry"> <div class="refnamediv"> <h1 class="refname">system</h1> <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">system</span> — <span class="dc-title">Execute an external program and display the output</span></p> </div> <div class="refsect1 description" id="refsect1-function.system-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">string</span> <span class="methodname"><strong>system</strong></span> ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$command</code></span> [, <span class="methodparam"><span class="type">int</span> <code class="parameter reference">&$return_var</code></span> ] )</div> <p class="para rdfs-comment"> <span class="function"><strong>system()</strong></span> is just like the C version of the function in that it executes the given <em><code class="parameter">command</code></em> and outputs the result. </p> <p class="para"> The <span class="function"><strong>system()</strong></span> call also tries to automatically flush the web server's output buffer after each line of output if PHP is running as a server module. </p> <p class="para"> 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> </div> <div class="refsect1 parameters" id="refsect1-function.system-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">return_var</code></em></span> <dd> <p class="para"> If the <em><code class="parameter">return_var</code></em> argument is present, 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.system-returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns the last line of the command output on success, and <strong><code>FALSE</code></strong> on failure. </p> </div> <div class="refsect1 examples" id="refsect1-function.system-examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example" id="example-3679"> <p><strong>Example #1 <span class="function"><strong>system()</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: #007700">echo </span><span style="color: #DD0000">'<pre>'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Outputs all the result of shellcommand "ls", and returns<br />// the last output line into $last_line. Stores the return value<br />// of the shell command in $retval.<br /></span><span style="color: #0000BB">$last_line </span><span style="color: #007700">= </span><span style="color: #0000BB">system</span><span style="color: #007700">(</span><span style="color: #DD0000">'ls'</span><span style="color: #007700">, </span><span style="color: #0000BB">$retval</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Printing additional info<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'<br /></pre><br /><hr />Last line of the output: ' </span><span style="color: #007700">. </span><span style="color: #0000BB">$last_line </span><span style="color: #007700">. </span><span style="color: #DD0000">'<br /><hr />Return value: ' </span><span style="color: #007700">. </span><span style="color: #0000BB">$retval</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.system-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.system-seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"> <span class="function"><a href="function.exec.html" class="function" rel="rdfs-seeAlso">exec()</a> - Execute an external program</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.popen.html" class="function" rel="rdfs-seeAlso">popen()</a> - Opens process file pointer</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> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.shell-exec.html">shell_exec</a></div> <div class="next" style="text-align: right; float: right;"><a href="book.pthreads.html">pthreads</a></div> <div class="up"><a href="ref.exec.html">Program execution Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div></body></html>