RegExp Pattern Matching Behavior

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

The following 3 patterns need to be matched with the common regexp mentioned below :

my $out1 = "Line 5 f3050_233_10_vserver_nfs_1 f3050_233_13_simple_aggr_raid4_1";

my $out2 = "Line 3 f3050_233_10_vserver_cifs_1 f3050_233_13_simple_aggr_raid4_1";

my $out3 = " Line 4 f3050_233_10_vserver_nfs_1 f3050_233_13_simple_aggr_raid4_1";

The regular expression is - /.*Line\s[3-30]\s+([\w-]+)\s+.*/i

This regular expression matches $out2 but not $out1 and $out3.

Im completely befuddled.
Advice is greatly appreciated!
Thanks.

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Re: RegExp Pattern Matching Behavior by kennethk (Abbot) on Jun 25, 2009 at 14:24 UTC
First, please wrap code in code tags (<code>, </code>) to maintain proper formatting - note how your square brackets got converted to links. Please read Writeup Formatting Tips. Your issue is that you expect `[3-30]` to match numbers 3-30, when you are performing what come down to complex string comparisons. The result of that particular group would be matching the character 3 (actually the range 3-3) or the character 0. If you substituted `/d{1,2}`, you would match any 1 or 2 digit sequence. If you really mean 3-30, you could use the more complex `(?:[3-9]\|[1-2]\d\|30)`. See perlreftut for more instruction on using regular expressions.	[reply] [d/l] [select]
Re^2: RegExp Pattern Matching Behavior by perlpal (Scribe) on Jun 25, 2009 at 14:37 UTC
With respect to 3-30 , i meant matching numbers between 3 and 30. In effect , i would be matching lines with line numbers from 3 to 30.	[reply]
Re^3: RegExp Pattern Matching Behavior by kennethk (Abbot) on Jun 25, 2009 at 14:44 UTC
You are still not using <code> tags. You've been around long enough you should know better. As I stated above, the expression `(?:[3-9]\|[1-2]\d\|30)` will match the numbers 3 through 30 inclusive. I used a non-capturing group to isolate the ors from the surrounding expressions and include three terms: `[3-9]` matches single digits 3-9; `[1-2]\d` matches single digits 1 or 2 followed by any digit, meaning 10-29; `30` matches 30.	[reply] [d/l] [select]
Re^4: RegExp Pattern Matching Behavior by perlpal (Scribe) on Jun 25, 2009 at 14:50 UTC
Re: RegExp Pattern Matching Behavior by ELISHEVA (Prior) on Jun 25, 2009 at 17:14 UTC
My apologies to kennethk it appears I did not read the thread carefully enough and he has already stated what is written below. `[3-30]` does not match line numbers 3 through 30. It matches a single character, either 3 or 0. Only one line `$out2` has either a 3 or 0 as its line number, hence that is the one that is matching. To match the numbers 3 through 30, you need a regular expression like this: `(?:[3-9]\|[12]\d\|30)`. To explain a bit: `(?:...)` is a "non-capturing" regular expression. That is, it matches a run of characters without stuffing the match into a variable. `\|` (the pipe) marks alternative regular expressions. Only one of the alternatives needs to match. `[...]` matches one among a list of alternative characters. Ranges of characters may be indicated using char dash char `\d` matches any digit, i.e. 0 through 9 Please see perlretut for a fuller explanation of each part of the regular expression. Best, beth	[reply] [d/l] [select]
Re^2: RegExp Pattern Matching Behavior by perlpal (Scribe) on Jun 26, 2009 at 06:14 UTC
to kennethk and beth , thank you for the regexp and the explanation.It solved a really big logic error in my code! Cheers!	[reply]
Re: RegExp Pattern Matching Behavior by Anonymous Monk on Jun 25, 2009 at 14:22 UTC
missing brackets in ..3-30.., this ways it will only match 3 followed by - etc.. the right is : `/.Line\s[3-30]\s+(\w-+)\s+./i`	[reply] [d/l]
Re^2: RegExp Pattern Matching Behavior by kennethk (Abbot) on Jun 25, 2009 at 14:46 UTC
Note that the OP has 3-30 (and not 3-30) in the regular expression because the poster included square brackets but forgot code tags.	[reply]
Re: RegExp Pattern Matching Behavior by Gyatso (Novice) on Jun 25, 2009 at 18:07 UTC
Regular expression: ^\s?Line\s{1}\d{1,}\s+[\w_\d]+\s+.* ^\s? ==> Starting with Zero or only one space \s{1} ==> Single space after "Line" \d{1,}==> Follwed by minimum one digit(maxm any no of digits) \s+ ==> Follwed by one or more number of spaces [\w_\d]+ ==> Follwed by any combination words,underscores and digits \s+ ==> Follwed by 1 or more number of spaces .* ==> Follwed by rest of the string Regards, Gytaso	[reply]