Perl regular expression rules

[wellmje]

Hello, I am looking for a way to validate that this use of regular expressions will match all and any commands except SU on a Red Hat Linux server when following Perl rules

 (?!.*/su[\r\s]).*/.*

Any assistance or direction would be appreciated. I know there are many other ways to achieve the same goal but I am being told that this should work. Thank You in advance!

[Crackers2]

You may want to give more details about what you're trying to accomplish, because...

[user@host]$ ll /bin/su
-rwsr-xr-x 1 root root 30148 Jul 21 19:54 /bin/su
[user@host]$ ln -s /bin/su notsu
[user@host]$ ./notsu
Password:
[root@host]#

So if you're trying to use this to prevent people from running su it's probably not a good idea.

[ww]

The best way to validate your regex is to read the docs re regexen; perlre, perlretut, etc (and there's lots of etc inside perldoc, too) and use the knowledge acquired to refine your ability to understand the regex.

Second best, perhaps? Seek out a regex explanation utility of the sort frequently mentioned here.

Next best, try it. Test (brute force) a substantial subset or all the commands you're likely to use, in a dry run setting like:

#pseudocode
my @commands=qw(ls rm rd cat....);

for $command(@commands) {
    if ($command =~ /(your regex here)/ ) {
        say "regex matched $command";
    } else {
         say "Oops! $command slipped by";
    }
}