Regex hackery

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

I have been thinking about a regular expression that can transform a list like this:

1. 10.Things.I.Hate.About.You[1999]DvDrip[Eng]-Ray 699.68 MB 
2. 100.Feet.2008.DvDRip-FxM 701.14 MB 
3. 11 - 14 1 286.22 MB 
4. 13_going_on_30(2004)[Brizzly] 700.23 MB 
...
1 523. Waz 699.93 MB 
1 524. We.Own.the.Night[2007]DvDrip[Eng]-Ray 700.87 MB 
1 525. Webs [2003]DVDRip[Xvid AC3[5.1]-RoCK&BlueLadyRG 1 347.70 MB
[download]

into:

10.Things.I.Hate.About.You[1999]DvDrip[Eng]-Ray,699.68 MB
100.Feet.2008.DvDRip-FxM,701.14
11 - 14,1286.22
13_going_on_30(2004)[Brizzly],700.23 
...
Waz,699.93
We.Own.the.Night[2007]DvDrip[Eng]-Ray,700.87
Webs [2003]DVDRip[Xvid AC3[5.1]-RoCK&BlueLadyRG,1347.70
[download]

Assumption : The filesize is never > 9999.99MB

So far I have a partially working regex:

^[^\.]+\. (.+?) (?:([0-9])(?: ))?([0-9]+\.[0-9]{2}) MB.*$

that maps to

$1:$2$3

to complete the transformation.

I used the colon because no desktop OS would allow that in a filename, so I am safe.

I built the regex without any formal method (i.e, via using intution) and that very same intution tells me this regex is horrifically complicated and slow!

I wish RegExBuddy had a online version or something similar.

How do I build a better RegEx for the same? Hints, tips...

Is there any free/open tool that will allow me to profile my regex (except writing a Perl script)?

Comment on Regex hackery Select or Download Code

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Re: Regex hackery by markkawika (Monk) on Jun 12, 2009 at 18:33 UTC
That regex isn't too bad. Your assumption about `:` not being allowed in a filename is completely wrong. About the only character not allowed in a filename is a directory separator, such as `/` on Unix. But apart from that, I have a few minor suggestions on your regex. Inside a character class `[]` a period does not need to be escaped. You should use `/x`. It makes your regex easier to read. `\d` is usually preferred to `[0-9]`. It makes your regex more portable. You have an unnecessary set of parens in your regex: `(?: )`. Rewritten, it would read: `/ ^ [^.]+ \. \s # Ignore the line numbers (.+?) # Capture the file name (?: (\d) \s # Capture the optional leading size digit ) ? ( \d+ \. \d {2} # Capture the rest of the size ) \s MB .* $ /x` [download] After this, your file name is `$1`, and your size is, as you stated, `$2$3`. And yes, there is an ambiguity, where if the line was: `1. go 2 123.45 MB` [download] The regex would parse "go" as the file name and "2123.45" as the file size. There's no way around this given the format of the input.	[reply] [d/l] [select]
Re^2: Regex hackery by ikegami (Patriarch) on Jun 12, 2009 at 18:46 UTC
Your assumption about : not being allowed in a filename is completely wrong. About the only character not allowed in a filename is a directory separator You're wrong about the OP being completely wrong. In Windows, the colon is the device indicator. On old Macs, the colon is the directory separator.	[reply]
Re: Regex hackery by ikegami (Patriarch) on Jun 12, 2009 at 18:03 UTC
Note that you will have ambiguities `3. go 2 286.22 MB` [download] `go 2,286.22 -or- go,2286.22` [download] I used the colon because no desktop OS would allow that in a filename, so I am safe. I guess you only tried the single one that doesn't allow you (Windows). All unixy system allows you to have colons in file names, incl linux and Macs. (Doh! I meant to call my Mac using roomy to confirm that the Mac desktop allows you to use colons before posting this, but it seems I submitted the post without even realising it. Feel free to correct me.)	[reply] [d/l] [select]
Re^2: Regex hackery by graff (Chancellor) on Jun 13, 2009 at 17:01 UTC
`$ uname -s Darwin $ touch test:file $ ls test:file test:file` [download] Yep, file names with colons are okay on macosx.	[reply] [d/l]
Re^3: Regex hackery by ikegami (Patriarch) on Jun 13, 2009 at 20:40 UTC
I asked about the GUI. I don't expect it to be any different, but the OP specifically talked about desktops.	[reply]
Re^4: Regex hackery by Your Mother (Archbishop) on Jun 14, 2009 at 05:07 UTC
Re: Regex hackery by planetscape (Chancellor) on Jun 13, 2009 at 12:27 UTC
Re^3: My Favourite Regex Tools (Was: Parsing a Variable Format String) may be of interest. Update: See also Visual REGEXP txt2re: headache relief for programmers :: regular expression generator HTH, planetscape	[reply]
Re^2: Regex hackery by PoorLuzer (Beadle) on Jun 14, 2009 at 00:53 UTC
Excellent stuff!	[reply]