private function getShell()
{
if (null !== self::$shell) {
return self::$shell;
}
self::$shell = false;
if (file_exists('/usr/bin/env')) {
// handle other OSs with bash/zsh/ksh/csh if available to hide the answer
$test = "/usr/bin/env %s -c 'echo OK' 2> /dev/null";
foreach (['bash', 'zsh', 'ksh', 'csh'] as $sh) {
if ('OK' === rtrim(shell_exec(sprintf($test, $sh)))) {
self::$shell = $sh;
break;
}
}
}
return self::$shell;
}