php-doc-en/reference/exec/functions/exec.xml
Victor Boivie 270fe8d301 fixed a typo
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@118162 c90b9560-bf6c-de11-be94-00142212c4b1
2003-02-26 06:12:25 +00:00

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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.5 $ -->
<!-- splitted from ./en/functions/exec.xml, last change in rev 1.2 -->
<refentry id="function.exec">
<refnamediv>
<refname>exec</refname>
<refpurpose>Execute an external program</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>string</type><methodname>exec</methodname>
<methodparam><type>string</type><parameter>command</parameter></methodparam>
<methodparam choice="opt"><type>array</type><parameter>output
</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>return_var</parameter></methodparam>
</methodsynopsis>
<para>
<function>exec</function> executes the given
<parameter>command</parameter>, however it does not output
anything. It simply returns 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>
If the <parameter>output</parameter> argument is present, then the
specified array will be filled with every line of output from the
command. Line endings, such as <literal>\n</literal>, are 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>
<para>
If the <parameter>return_var</parameter> argument is present
along with the <parameter>array</parameter> argument, then the
return status of the executed command will be written to this
variable.
</para>
<warning>
<para>
If you are going to allow data coming from user input to be passed to
this function, then you should be using
<function>escapeshellarg</function> or
<function>escapeshellcmd</function> to make sure that users cannot trick
the system into executing arbitrary commands.
</para>
</warning>
<note>
<para>
If you start a program using this function and want to leave it running
in the background, you have to make sure that the output of that program
is redirected to a file or some other output stream or else PHP will
hang until the execution of the program ends.
</para>
</note>
<para>
See also <function>system</function>,
<function>passthru</function>, <function>popen</function>,
<function>escapeshellcmd</function>, and the <link
linkend="language.operators.execution">backtick operator</link>.
</para>
</refsect1>
</refentry>
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