Program execution Functions
PHP Manual

escapeshellcmd

Escape shell metacharacters

Description

string escapeshellcmd(string $command)

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 (^).

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));

See Also