Regular Expression Assistance

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

I have the following line of code in a script:

.Pattern = "(^c|l|j|s|o)\d{4}[_](\d*?.dat|\d*?.idx)"

This is being used to delete any files starting with C, L, J, S or O followed by the '_' and 0 or more digits then the extension. My issue is I need to modify this single line to delete all files as stated above AND files that do not have the '_' and 0 or more numbers in it.

Problem is I do not want to delete a files named C1234ABC.IDX. 1 letter, 4 digits, followed by either the extension, or _# or _## then extension. I have been playing around with:

.Pattern = "(^c|l|j|s|o)\d{4}\w*?(\d*?.dat|\d*?.idx)"

but this did not do anything at all. Any ideas or suggestions to help resolve this would be great.

Thanks!!

Comment on Regular Expression Assistance Select or Download Code

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Re: Regular Expression Assistance by toolic (Bishop) on May 17, 2013 at 20:14 UTC
Not sure I follow, but you can build on this: `use warnings; use strict; while (<DATA>) { chomp; if (/ ^ [cljso] \d{4} _ \d*? \. (dat\|idx) $ /ix) { print "$_ : match\n"; } else { print "$_ : no match\n"; } } __DATA__ C1234ABC.IDX C1234_ABC.IDX C1234_.IDX` [download] prints: `C1234ABC.IDX : no match C1234_ABC.IDX : no match C1234_.IDX : match` [download]	[reply] [d/l] [select]
Re: Regular Expression Assistance by Laurent_R (Canon) on May 17, 2013 at 20:51 UTC
So you want to match: C1234_.IDX, C1234_45.IDX and C1234.IDX but not C1234ABC.IDX. Is this correct? If so, the pattern could be something like this : `/^([cljso]\d{4}(_\d*)?\.(dat\|idx))$/` i.e. start of string, one of the five letters cljso, 4 digits, an optional ("_" followed by any number of digits), followed by a dot and an extension chosen among dat and idx at the end of the string. If this is not what you need, please be clearer on your requirement.	[reply] [d/l]
Re: Regular Expression Assistance by frozenwithjoy (Priest) on May 17, 2013 at 22:32 UTC
You should plug your regex pattern into this regex visualization tool. It will help you see some problems with your pattern. For example, your `^` indicator for beginning of line is only applying to the `c`, not `ljso`.	[reply] [d/l] [select]
Re^2: Regular Expression Assistance by Laurent_R (Canon) on May 17, 2013 at 22:39 UTC
This tool is just great. I have just bookmarked it, I am sure it will be useful to me.	[reply]
Re: Regular Expression Assistance (data?) by LanX (Saint) on May 17, 2013 at 20:29 UTC
Hmm ... could you please provide desired input and output data? That would facilitate finding a real solution w/o spending time on speculative stuff. BTW I don't understand why `.Pattern` starts with a dot, this is not Perl syntax. Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l]
Re: Regular Expression Assistance by eye (Chaplain) on May 18, 2013 at 18:40 UTC
Some good suggestions above. As long as we are commenting on a regex that is assigned to a variable, we should mention that the `qr` quoting operator will create a compiled regex.	[reply]