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Old 04-22-2005, 03:04 AM   #1
smart_sagittari
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Using regular expression in filename



I have a script which gets as input a filename and does a grep on that. Now the problem is something like this:

The files I need to look in for the pattern are named as follows:

out, out.20050421.1234, out.20050421.2134, out.20050420.0012

My program gets as input the filename upto before the last . [DOT], like either, out [for the first file] or out.20050421 for the second and third files.

Now, in the second case [file name input out.20050421], I directly can use grep pattern out.20050421.[0-9]* to get results from the second and third files stated above [desired output]

However, if I get the filename as out, doing a out[0-9]* doesnt work [I dont know why]

Can someone give me a solution to this[assuming that I have not confused people enough]!!!

Last edited by smart_sagittari; 04-22-2005 at 03:31 AM.
 
Old 04-23-2005, 11:56 AM   #2
jailbait
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"However, if I get the filename as out, doing a out[0-9]* doesnt work [I dont know why]"
Are you mising a period?
Shouldn't that be out.[0-9]*

------------------------------
Steve Stites
 
Old 04-24-2005, 11:02 PM   #3
smart_sagittari
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Thats the problem. The base file doesnt have a . [DOT]. How can I go abt this. Is there some way I can include a . inside the brackets [so as to consider it an optional dot]?
 
Old 04-25-2005, 02:02 AM   #4
Dark_Helmet
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I'm not sure your wildcard is doing what you hope it does (assuming this is a shell script and not perl).

In the shell, using "[0-9]*" says there must be a single character between 0 and 9 (inclusive), followed by any number of other characters. In other words, "out[0-9]*" would match:
out0
out1
out2a
out3abc
out456z
...

It's not the same behavior as you'd get from a traditional regular expression.

You might want to consider using the '?' wildcard, but I don't know if that would really solve the problem.
 
Old 04-25-2005, 02:09 AM   #5
smart_sagittari
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Thanks for the suggestion. I shall certainly have a look into it.
 
Old 04-25-2005, 02:20 AM   #6
Dark_Helmet
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If you're using Bash, you'll be interested to read the secion regarding "pathname expansion". Specifically, the pattern matching sub-section. It explains how the wildcards work. In addition to the basic wildcards (*, ?, [] ), there are some expressions that have similar effects as traditional regular expressions. For instance:
Code:
       If the extglob shell option is enabled using the shopt builtin, several
       extended pattern matching operators are recognized.  In  the  following
       description, a pattern-list is a list of one or more patterns separated
       by a |.  Composite patterns may be formed using one or more of the fol-
       lowing sub-patterns:

              ?(pattern-list)
                     Matches zero or one occurrence of the given patterns
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns
              +(pattern-list)
                     Matches one or more occurrences of the given patterns
              @(pattern-list)
                     Matches exactly one of the given patterns
              !(pattern-list)
                     Matches anything except one of the given patterns
That's from my man page (bash version 3).

Last edited by Dark_Helmet; 04-25-2005 at 02:22 AM.
 
  


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