in reply to Grepping with Perl: How to stop after first match?

Assuming you are reading your input file in a while loop you could try this.

while ( <$inFH> )
{
    m#cpuinfo\nvendor_id\s+:\s(.*?)\n#
       and print "CPU:\t$1" and last;
}

[download]

I hope this is helpful.

Cheers,

JohnGG

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Re^2: Grepping with Perl: How to stop after first match?
by paulnovl (Novice) on Dec 07, 2007 at 11:08 UTC
    Thanks for the suggestion, but as I'm not reading the input in a loop, I can't see a way to implement it.
    My input is in the form of a stream consisting of many tar'ed text files written to standard-out when they're extracted by bzcat (from .tar.bz2 files).
    I'm trying to use perl to do the grepping, but that's only a part of a larger shell script that looks something like this (snipped for clarity): 
    #! /bin/sh

## other stuff happens here, but snipped for clarity

scdir=/var/log

find $scdir -type f -name "nts_*.bz2" |    # find interesting files in
+ $scdir
  perl -wnl -e '7 > -M and print;' |        # ignore old files
    xargs bzcat -k |                # unpack contents to STDOUT
      perl -wn00 -e '                # paragraph mode

    m[kernel\.hostname\s.\s(.*?)\n] and print "Hostname:\t$1\n";    # 
+grep for hostname
    m[\/bin\/date\n(.*?)\n] and print "Generated:\t$1\n";    # grep fo
+r date

        ## I grep for other stuff here, but snipped for clarity

        m[Settings.for\s(.*?):\n] and print "Interface:\t$1\n";    # g
+rep for eth interfaces

        m[Speed:\s(.*?)Mb\/s] and            # grep for interface spee
+d
        print "\ -speed:\t$1Mb\/s\n" ;

    m[Duplex:\s(.*?)\n] and                # grep for interface duplex
        print "\ -duplex:\t$1\n" ;

        m[Auto-negotiation:\s(.*?)\n] and        # grep for interface 
+autoneg
        print "\ -autoneg:\t$1\n" ; 

    m[cpuinfo\nvendor_id\s+:\s(.*?)\n] and        # grep for cpu id
      print "CPU:\t\t$1\n" ;

      '
exit $!

    [download]

    I'm a Perl novice, so am open to suggestions that I'm not approaching this the right way.
[reply]
[d/l]
      My first thought is, "no, you're probably not using the right tools for what you want to do."

      I would attempt the whole thing in Perl for starters. Have a look at opendir, readdir and closedir along with grep for finding the compressed tar archives you want to work with and placing the names in an array. Having found them I would then loop over them using CPAN modules to uncompress (Compress::Bzip2) and read (Archive::Tar) the archives. I would read each file in the archive into a string so that I could do as many or as few matches as I wanted.

      I should stress that I have never done anything like this before but I think you are more likely to meet with success by adopting this approach. I hope these thoughts will help you towards a solution but feel free to ask further if things aren't clear.

      Cheers,

      JohnGG

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