(PHP 4, PHP 5, PHP 7, PHP 8)
escapeshellcmd — Escape shell metacharacters
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().
commandThe command that will be escaped.
The escaped string.
Throws a ValueError if command
contains null bytes, or if command or the escaped
command is longer than the maximum command line length allowed by the
system.
| Version | Description |
|---|---|
| 8.4.0 |
If command or the escaped command is too long,
escapeshellcmd() now throws a ValueError.
Previously a fatal E_ERROR was raised.
|
| 8.0.0 |
If command contains null bytes,
escapeshellcmd() now throws a ValueError.
Previously a fatal E_ERROR was raised.
|
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);
?>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.
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));