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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- splitted from ./en/functions/exec.xml, last change in rev 1.2 -->
<refentry xml:id="function.exec" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>exec</refname>
<refpurpose>Execute an external program</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type class="union"><type>string</type><type>false</type></type><methodname>exec</methodname>
<methodparam><type>string</type><parameter>command</parameter></methodparam>
<methodparam choice="opt"><type>array</type><parameter role="reference">output</parameter><initializer>&null;</initializer></methodparam>
<methodparam choice="opt"><type>int</type><parameter role="reference">result_code</parameter><initializer>&null;</initializer></methodparam>
</methodsynopsis>
<para>
<function>exec</function> executes the given
<parameter>command</parameter>.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>command</parameter></term>
<listitem>
<para>
The command that will be executed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>output</parameter></term>
<listitem>
<para>
If the <parameter>output</parameter> argument is present, then the
specified array will be filled with every line of output from the
command. Trailing whitespace, such as <literal>\n</literal>, is not
included in this array. Note that if the array already contains some
elements, <function>exec</function> will append to the end of the array.
If you do not want the function to append elements, call
<function>unset</function> on the array before passing it to
<function>exec</function>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>result_code</parameter></term>
<listitem>
<para>
If the <parameter>result_code</parameter> argument is present
along with the <parameter>output</parameter> argument, then the
return status of the executed command will be written to this
variable.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<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 <function>passthru</function> function.
</para>
<para>
Returns &false; on failure.
</para>
<para>
To get the output of the executed command, be sure to set and use the
<parameter>output</parameter> parameter.
</para>
</refsect1>
<refsect1 role="errors">
&reftitle.errors;
<para>
Emits an <constant>E_WARNING</constant> if <function>exec</function>
is unable to execute the <parameter>command</parameter>.
</para>
<para>
Throws a <classname>ValueError</classname> if <parameter>command</parameter>
is empty or contains null bytes.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>8.0.0</entry>
<entry>
If <parameter>command</parameter> is empty or contains null bytes,
<function>exec</function> now throws a <classname>ValueError</classname>.
Previously it emitted an <constant>E_WARNING</constant> and returned &false;.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title>An <function>exec</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// outputs the username that owns the running php/httpd process
// (on a system with the "whoami" executable in the path)
$output=null;
$retval=null;
exec('whoami', $output, $retval);
echo "Returned with status $retval and output:\n";
print_r($output);
?>
]]>
</programlisting>
&example.outputs.similar;
<screen>
<![CDATA[
Returned with status 0 and output:
Array
(
[0] => cmb
)
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
&warn.escapeshell;
¬e.exec-bg;
¬e.exec-bypass-shell;
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>system</function></member>
<member><function>passthru</function></member>
<member><function>escapeshellcmd</function></member>
<member><function>pcntl_exec</function></member>
<member><link linkend="language.operators.execution">backtick operator</link></member>
</simplelist>
</para>
</refsect1>
</refentry>
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