PHP exec - check if enabled or disabled

问题:

Is there a way to check in a php script if exec() is enabled or disabled on a server?

回答1:

if(function_exists('exec')) {
    echo "exec is enabled";
}

回答2:

This will check if the function actually works (permissions, rights, etc):

if(exec('echo EXEC') == 'EXEC'){
    echo 'exec works';
}

回答3:

ini_get('disable_functions')

What you actually want to do is use ini_get('disable_functions') to find out if it is available to you:

<?php
function exec_enabled() {
    $disabled = explode(',', ini_get('disable_functions'));
    return !in_array('exec', $disabled);
}
?>

Answered on stackoverflow here: Check if "exec" is disabled, Which actually seems to come from the PHP Man page: http://php.net/manual/en/function.exec.php#97187

Path

If the above returns true (you can use exec()), but PHP can still not trigger the script there is a good chance that you have a path issue for that script, test this by doing:

print exec('which bash');

and then try

print exec('which ogr2ogr');

回答4:

This will check that exec is available and enabled BEFORE trying to run it. If you run exec() and the function does not exist or is disabled a warning will be generated. Depending on the server settings that may render to the browser and will almost-always write a line to a log file = performance hit.

// Exec function exists.
// Exec is not disabled.
// Safe Mode is not on.
$exec_enabled =
   function_exists('exec') &&
   !in_array('exec', array_map('trim', explode(', ', ini_get('disable_functions')))) &&
   strtolower(ini_get('safe_mode')) != 1
;


if($exec_enabled) { exec('blah'); }

回答5:

It's a bit tricky to find exec function available until unless checking all possibilities

1.function_exist('exec')

2.Scanning through ini_get('disabled_functions)

3.Checking safe_mode enabled

function is_shell_exec_available() {
    if (in_array(strtolower(ini_get('safe_mode')), array('on', '1'), true) || (!function_exists('exec'))) {
        return false;
    }
    $disabled_functions = explode(',', ini_get('disable_functions'));
    $exec_enabled = !in_array('exec', $disabled_functions);
    return ($exec_enabled) ? true : false;
}

This function never throws warnings unless ini_get function not disabled.

回答6:

Example:

if(strpos(ini_get('disable_functions'),'ini_set')===false) 
    @ini_set('display_errors',0);

回答7:

This is some ugly code I made to detect if a function is enabled or not.

function is_enabled($f)
{
    if($f=='ini_get')return@ini_get('a')===false;
    return(($l=@ini_get('disable_functions'))===null||!is_callable($f)||!function_exists($f)||!in_array($f,array_map('trim',explode(',',$l)));
}

//Usage example:
print_r(is_enabled('str_split'));//true or null if ini_get() is disabled

回答8:

I am assuming that you are running this on a linux server.

You could test the exec function by running the following php script:

exec("whoami", $ret);

echo $ret[0];

This will return the command whoami.

If it errors out, it is because the exec function could not run.