regexp to check if file name matches pattern

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

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Re: regexp to check if file name matches pattern by davido (Cardinal) on Feb 24, 2009 at 22:07 UTC
Perhaps this: `/^SYS(?:[^%]+%)+[^.]*\.pdf/i` [download] Matches SYS followed by any non % character(s) that are followed by a % (can be repeated), followed by just about anything except a dot (.) (that's where the date field goes), followed by dot pdf. Update: `/i` added, because when I see SYS and .pdf (upper, and lower) I start thinking that case probably shouldn't be allowed to foul up a match. Dave	[reply] [d/l] [select]
Re^2: regexp to check if file name matches pattern by smanicka (Scribe) on Feb 24, 2009 at 22:11 UTC
the systemblahblah can contain a period unfortunately	[reply]
Re^3: regexp to check if file name matches pattern by davido (Cardinal) on Feb 24, 2009 at 22:15 UTC
I didn't preclude the dot from "systemblah%blah%", I precluded dot from the datestamp. Did you try it yet? There may be other errors, but that one isn't. ;) Dave	[reply]
Re: regexp to check if file name matches pattern by Marshall (Canon) on Feb 24, 2009 at 23:22 UTC
An alternate solution (there are many): `$file= "SYSB_A31.GROUPINS%RDEBLIST%REAPPLY%2008.12.16.20.31.35.pdf"; if ($file =~ /^SYS[\w.]+%[\w.]+%[\w.]+%[0-9.]+.pdf/) {print "yes"} else {print "no"} #prints yes` [download] A set of characters is enclosed in []. \w are the "word chars" and we add the "dot" to that set by \w.+. Same idea with 0-9.+. Other solution that has `[^%]+` is good too. That means anything except %. Take your pick.	[reply] [d/l] [select]
Re: regexp to check if file name matches pattern by smanicka (Scribe) on Feb 24, 2009 at 22:24 UTC
Hello Dave, it doesn't work.I tried: `#!/usr/bin/perl $file= "SYSB_A31.GROUPINS%RDEBLIST%REAPPLY%2008.12.16.20.31.35.pdf"; if ($file=~ /^SYS(?:[^%]+%)+[^.]*\.pdf/i){ print "yes"; } else{ print "no"; }` [download] and it prints out no. Thanks Smanicka	[reply] [d/l]
Re^2: regexp to check if file name matches pattern by davido (Cardinal) on Feb 24, 2009 at 22:34 UTC
Lol, I had no way of knowing that your date field was "dot delimited." My solution would naturally reject that. Here's a new approach that should do the trick given that new, previously unmentioned requirement. `/^SYS(?:[^%]+%){2,}[\d.]+\.pdf/i` [download] Let me know how that works out. This time I'm specifically allowing the 'dot' delimiter in the date field. This solution is going to result in some backtracking though. It might be better written as: `/^SYS(?:[^%]+%){2,}(?:\d+)(?:.\d+)+\.pdf/i` [download] This will get less backtracking, and thus should be a little more efficient, if that matters. Dave	[reply] [d/l] [select]
Re^2: regexp to check if file name matches pattern by smanicka (Scribe) on Feb 24, 2009 at 22:28 UTC
tried {2,} instead of + as suggested.since prints out no	[reply]
Re: regexp to check if file name matches pattern by Grey Fox (Chaplain) on Feb 25, 2009 at 18:13 UTC
Howdy; I have posted in the past a great tool for explaining regexe's called My REGEX Tester. I have a link to it in Found new online Regex tool. Plus there is a nice website called Regular-Expressions Quickstart. Which teaches all of the basics of REGEX. Teach a person to fish and you feed them for a lifetime. -- Grey Fox "We are grey. We stand between the darkness and the light" B5	[reply]