Who said regular expressions can’t do that?
Courtesy of my employer, Salir.com, here’s a PHPUnit test which does such validation. Feel free to modify & distribute. I’ll appreciate if you keep the @author notice & link to web site.
<?php
/**
* @author Jordi Salvat i Alabart - with thanks to <a href="www.salir.com">Salir.com</a>.
*/
abstract class CrontabChecker extends PHPUnit_Framework_TestCase {
protected function assertFileIsValidUserCrontab($file) {
$f= @fopen($file, 'r', 1);
$this->assertTrue($f !== false, 'Crontab file must exist');
while (($line= fgets($f)) !== false) {
$this->assertLineIsValid($line);
}
}
protected function assertLineIsValid($line) {
$regexp= $this->buildRegexp();
$this->assertTrue(preg_match("/$regexp/", $line) !== 0);
}
private function buildRegexp() {
$numbers= array(
'min'=>'[0-5]?\d',
'hour'=>'[01]?\d|2[0-3]',
'day'=>'0?[1-9]|[12]\d|3[01]',
'month'=>'[1-9]|1[012]',
'dow'=>'[0-7]'
);
foreach($numbers as $field=>$number) {
$range= "($number)(-($number)(\/\d+)?)?";
$field_re[$field]= "\*(\/\d+)?|$range(,$range)*";
}
$field_re['month'].='|jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec';
$field_re['dow'].='|mon|tue|wed|thu|fri|sat|sun';
$fields_re="(".join(')\s+(', $field_re).')';
$replacements="@reboot|@yearly|@annually|@monthly|@weekly|@daily|@midnight|@hourly";
return '^\s*('.
'$'.
'|#'.
'|\w+\s*='.
"|$fields_re\s+\S".
"|($replacements)\s+\S".
')';
}
}