Quickie regular expression question.

rementis has asked for the wisdom of the Perl Monks concerning the following question:

OK, all-knowing Monks...

I am trying to determine if a variable contains ONLY letters and numbers. If there are any characters besides letters and digits I want the test to fail. I'm using this code and it's not working:

if ($newpasswd !~ /[A-Za-z0-9]/) {
     EXECUTE SOME THINGS;
                                 }
[download]

(There is a bracket before the A and after the 9, but it's not showing up in this web page for some reason.)

Any ideas are welcome, thanks!

20050316 Edit by ysth: p & code tags

Comment on Quickie regular expression question. Download Code

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Re: Quickie regular expression question. by ikegami (Patriarch) on Mar 16, 2005 at 17:16 UTC
`$newpasswd !~ /[A-Za-z0-9]/` means "doesn't contain letters or digits". You want `$newpasswd !~ /^[A-Za-z0-9]*$/` ("isn't a string of just letters and digits") or even `$newpasswd !~ /^[A-Za-z0-9]{6,}$/` ("isn't a string of 6 or more letters and digits") to check for a minumum length of 6 at the same time. By the way, why are you restricting the password to those characters? It looks like you're weakening security for nothing.	[reply] [d/l] [select]
Re: Quickie regular expression question. by RazorbladeBidet (Friar) on Mar 16, 2005 at 17:16 UTC
You want `if ( $newpasswd !~ /^[A-Za-z0-9]+$/ ) { # blah }` [download] (if you want the "blah" to execute when the variable contains anything EXCEPT ALL letters and/or numbers) -------------- It's sad that a family can be torn apart by such a such a simple thing as a pack of wild dogs	[reply] [d/l]
Re: Quickie regular expression question. by holli (Abbot) on Mar 16, 2005 at 17:18 UTC
the some reason is that you are not using code-tags. As for your question, your code only checks for a single occurence of a digit/letter. Change it to `if ($newpasswd !~ /^[A-Za-z0-9]+$/) { #EXECUTE SOME THINGS; }` [download] or even `if ($newpasswd !~ /^[\w\d]+$/) { #EXECUTE SOME THINGS; }` [download] holli, /regexed monk/	[reply] [d/l] [select]
Re^2: Quickie regular expression question. by ikegami (Patriarch) on Mar 16, 2005 at 17:28 UTC
`[\w\d]` is a much bigger set. It includes "_" and the chinese character for "one", for example.	[reply] [d/l]
Re^2: Quickie regular expression question. by Fletch (Bishop) on Mar 16, 2005 at 17:36 UTC
`[:alnum:]` would be better than `\w\d` as that's strictly alphanumerics and should respect locale as well.	[reply] [d/l] [select]
Re: Quickie regular expression question. by saintmike (Vicar) on Mar 16, 2005 at 17:19 UTC
What you're testing is if `$newpasswd` doesn't contain any characters from the range `[A-Za-z0-9]`. What you want instead, is testing if `$newpasswd` does contain any characters outside the character class `[A-Za-z0-9]`, and then negate the test: `if ($newpasswd !~ /[^A-Za-z0-9]/) { # EXECUTE SOME THINGS; }` [download]	[reply] [d/l] [select]
Re: Quickie regular expression question. by sh1tn (Priest) on Mar 16, 2005 at 17:53 UTC
`if ($newpasswd =~ /(?:\W\|_)/) { # EXECUTE SOME THINGS }` [download]	[reply] [d/l]
Re: Quickie regular expression question. by rementis (Beadle) on Mar 16, 2005 at 17:48 UTC
I knew it would be something simple, I really need to get Mastering Regular Expressions. Thanks!	[reply]