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haimat
Apprentice
Joined: 05 Sep 2002
Posts: 239
Location: Vienna / Austria
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 Posted: Thu May 08, 2003 1:00 pm Post subject: perl and regular expression |
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Hi all,
I have a small problem with perl and a RE. I have a file with this content:
| Code: | test 12345
test2 3423423
test3 2342342
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I want to extract the line with "test" and only "test" (so not "test2" and/or "test3"). I tried it with
but that doesn't work 
What did I wrong - has anyone an idea? Greets and TIA, Matthias |
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erebus
n00b
Joined: 17 May 2002
Posts: 49
Location: United Kingdom
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| Posted: Thu May 08, 2003 2:11 pm Post subject: |
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Hi ya,
Sorry about being a bit vague but I'm more or a tcl man when it comes to regular expressions... Anyway I had a quick go managed to get this bit of code to produce the rest you are looking for
[code]grep "test[[:space]]"[\code]
So I'm guessing that something is wrong with you're regular expression syntax's for a space... |
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haimat
Apprentice
Joined: 05 Sep 2002
Posts: 239
Location: Vienna / Austria
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| Posted: Thu May 08, 2003 2:29 pm Post subject: |
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hmm... it doesn't work even if I try it with
| Code: | grep "test[\s]+"
grep "test[ ]+"
grep "test +"
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with none of these
but if i do a
then I get all three lines... |
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guero61
l33t
Joined: 14 Oct 2002
Posts: 811
Location: Behind you
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| Posted: Thu May 08, 2003 2:48 pm Post subject: |
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| Is the whitespace always a space or can it be a tab (^I)? If you can count on it being a space, you can just put 'test ' and it'll find it for you. |
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haimat
Apprentice
Joined: 05 Sep 2002
Posts: 239
Location: Vienna / Austria
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| Posted: Thu May 08, 2003 3:01 pm Post subject: |
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ohh I tried it with
as well, but as you guess ... that doesn't work either |
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Naan Yaar
Bodhisattva
Joined: 27 Jun 2002
Posts: 1549
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| Posted: Thu May 08, 2003 3:23 pm Post subject: |
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When I do:
| Code: |
perl -e 'print grep /this\s+/, <>;' < test
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where test is:
| Code: |
this aaa
this2 aaa
this3 bbb
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I get:
Seems to work fine. |
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haimat
Apprentice
Joined: 05 Sep 2002
Posts: 239
Location: Vienna / Austria
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| Posted: Thu May 08, 2003 4:02 pm Post subject: |
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ok, seems I made a mistake. It works with
thx for all your input! Greets, Matthias |
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dma
Guru
Joined: 31 Jan 2003
Posts: 437
Location: Charlotte, NC, USA
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| Posted: Thu May 08, 2003 4:20 pm Post subject: |
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Your problem is that you used doublequotes, within which the backslash has special meaning for the shell itself. Try using single quotes or putting a backslash before your backslash:
| Code: | grep "test\\s+"
grep 'test\s+'
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ferringb
Retired Dev
Joined: 03 Apr 2003
Posts: 357
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| Posted: Thu May 08, 2003 5:40 pm Post subject: |
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Something nifty to use also- zero-width positive look ahead.
an example using you're data listed
...grep (/test(?=\s)/, @data)...
This will match test followed by whitespace, but nothing else. Take a look in the man page perlre for some of the other fun options (zero width negative look ahead- matching something that *isn't* followed by something). |
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guero61
l33t
Joined: 14 Oct 2002
Posts: 811
Location: Behind you
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| Posted: Thu May 08, 2003 11:00 pm Post subject: |
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| dma wrote: | Your problem is that you used doublequotes, within which the backslash has special meaning for the shell itself. Try using single quotes or putting a backslash before your backslash:
| Code: | grep "test\\s+"
grep 'test\s+'
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The only problem is, he's not shelling out -- grep is a function in Perl that does the same action, just on an array or such instead of a file.
That said, I was kinda wondering why you weren't using /pattern/, but I figured you knew best -- I've had to mix /pattern/ and "pattern" as well as 'pattern' many times in Perl. |
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