escapeshellcmd
(PHP 4, PHP 5, PHP 7, PHP 8)
escapeshellcmd — Escape shell metacharacters
Description
escapeshellcmd() escapes any characters in a
string that might be used to trick a shell command into executing
arbitrary commands. This function should be used to make sure
that any data coming from user input is escaped before this data
is passed to the exec() or
system() functions, or to the backtick
operator.
Following characters are preceded by a backslash:
&#;`|*?~<>^()[]{}$\, \x0A
and \xFF. ' and "
are escaped only if they are not paired. On Windows, all these characters
plus % and ! are preceded by a caret
(^).
The behavior of this function with multibyte strings depends on the current
LC_CTYPE locale setting. Unrecognized characters will be
discarded. See setlocale().
Parameters
command-
The command that will be escaped.
Return Values
The escaped string.
Examples
Example #1 escapeshellcmd() example
<?php
// We allow arbitrary number of arguments intentionally here.
$command = './configure '.$_POST['configure_options'];
$escaped_command = escapeshellcmd($command);
system($escaped_command);
?>
Notes
Warning
escapeshellcmd() should be used on the whole
command string, and it still allows the attacker to pass
arbitrary number of arguments. For escaping a single argument
escapeshellarg() should be used instead.
Warning
Spaces will not be escaped by escapeshellcmd()
which can be problematic on Windows with paths like:
C:\Program Files\ProgramName\program.exe.
This can be mitigated using the following code snippet:
<?php
$cmd = preg_replace('`(?<!^) `', '^ ', escapeshellcmd($cmd));
escapeshellarg
Program execution Functions