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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Execute an external program and display the output</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="ref.exec.html">Program execution Functions</a></div> <div class="next" style="text-align: right; float: right;"><a href="book.expect.html">Expect</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"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">string</span> <span class="methodname"><b><b>system</b></b></span> ( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$command</tt></span> [, <span class="methodparam"><span class="type">int</span> <tt class="parameter reference">&$return_var</tt></span> ] )</div> <p class="para rdfs-comment"> <b>system()</b> is just like the C version of the function in that it executes the given <i><tt class="parameter">command</tt></i> and outputs the result. </p> <p class="para"> The <b>system()</b> 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 <a href="function.passthru.html" class="function">passthru()</a> function. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">command</tt></i></span> <dd> <p class="para"> The command that will be executed. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">return_var</tt></i></span> <dd> <p class="para"> If the <i><tt class="parameter">return_var</tt></i> 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"> <h3 class="title">Return Values</h3> <p class="para"> Returns the last line of the command output on success, and <b><tt>FALSE</tt></b> on failure. </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 <b>system()</b> example</b></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"> <h3 class="title">Notes</h3> <div class="warning"><b class="warning">Warning</b><p class="para">When allowing user-supplied data to bepassed to this function, use<a href="function.escapeshellarg.html" class="function">escapeshellarg()</a> or <a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a>to ensure that users cannot trick the system into executing arbitrarycommands.</p></div> <blockquote><p><b class="note">Note</b>: If a program is started with this function,in order for it to continue running in the background, the output of theprogram must be redirected to a file or another output stream. Failing to do sowill cause PHP to hang until the execution of the program ends.<br /></p></blockquote> <blockquote><p><b class="note">Note</b>: <span class="simpara">When<a href="features.safe-mode.html" class="link">safe mode</a> is enabled, you can onlyexecute files within the <a href="features.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 <i>..</i>components in the path to the executable.</span></p></blockquote> <div class="warning"><b class="warning">Warning</b><p class="simpara">With <a href="features.safe-mode.html" class="link">safe mode</a> enabled,the command string is escaped with <a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a>. Thus, <i>echo y | echo x</i> becomes <i>echo y \| echo x</i>.</p></div> </div> <div class="refsect1 seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><a href="function.exec.html" class="function" rel="rdfs-seeAlso">exec()</a></li> <li class="member"><a href="function.passthru.html" class="function" rel="rdfs-seeAlso">passthru()</a></li> <li class="member"><a href="function.popen.html" class="function" rel="rdfs-seeAlso">popen()</a></li> <li class="member"><a href="function.escapeshellcmd.html" class="function" rel="rdfs-seeAlso">escapeshellcmd()</a></li> <li class="member"><a href="function.pcntl-exec.html" class="function" rel="rdfs-seeAlso">pcntl_exec()</a></li> <li class="member"><a href="language.operators.execution.html" class="link">backtick operator</a></li> </ul> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="ref.exec.html">Program execution Functions</a></div> <div class="next" style="text-align: right; float: right;"><a href="book.expect.html">Expect</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>⌨️ 快捷键说明
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