Validating Crontab Entries with PHP

Question

What is the best way to validate a crontab entry with PHP? Should I be using a regex, or an external library? I\'ve got a PHP script that adds/removes entries from a crontab

Answer 1

Thanks to Jordi Salvat i Alabart and ph4r05.

I have small modified existing solution posted on php. Perl alternative to generate regex:

sub _BuildRegex {
    my $number = {
            'min'   =>      '[0-5]?\d',
            'hour'  =>      '[01]?\d|2[0-3]',
            'day'   =>      '0?[1-9]|[12]\d|3[01]',
            'month' =>      '[1-9]|1[012]',
            'dow'   =>      '[0-6]'
    };

    my $field_re = {};
    foreach my $nmb ( qw/min hour day month dow/ ) {
            my $range = "(?:$number->{$nmb})(?:-(?:$number->{$nmb})(?:\\/\\d+)?)?";
            $field_re->{$nmb} = "\\*(?:\\/\\d+)?|$range(?:,$range)*";
    }

    $field_re->{'month'} .='|[jJ]an|[fF]eb|[mM]ar|[aA]pr|[mM]ay|[jJ]un|[jJ]ul|[aA]ug|[sS]ep|[oO]ct|[nN]ov|[dD]ec';
    $field_re->{'dow'} .= '|[mM]on|[tT]ue|[wW]ed|[tT]hu|[fF]ri|[sS]at|[sS]un';

    my $ff = [];
    push @$ff, $field_re->{$_} foreach ( qw/min hour day month dow/ );

    my $fields_req = '(' . join(')\s+(', @$ff) . ')';

    my $replacements = '@reboot|@yearly|@annually|@monthly|@weekly|@daily|@midnight|@hourly';

    return '^\s*(' .
         '$' .
         '|#' .
         '|\w+\s*=' .
         "|$fields_req\\s+" .
         "|($replacements)\\s+" .
         ')' .
         '([^\\s]+)\\s+' .
         '(.*)$';
}