Re: Grepping with Perl: How to stop after first match?

People seem to have missed that you are looking for "2-line strings". Reading and matching one line at a time won't succeed.

You need to maintain a rolling two-line buffer to do this.

...## get $fh from somewhere (eg.open)
my $last = '';
while( <$fh> ) {
    ( $last . $_ ) =~ m[cpuinfo\nvendor_id\s+:\s(.*?)\n] 
        and print qq[CPU:$1] and last; 
    $last = $_;
}
...
[download]

Or as a (longish) one-liner

perl -ne"($last.$_)=~m[cpuinfo\nvendor_id\s+:\s(.*?)\n]&&print qq[CPU:
+$1]&&exit;$last=$_" yourfile
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Re^2: Grepping with Perl: How to stop after first match?
by paulnovl (Novice) on Dec 07, 2007 at 11:22 UTC

#! /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]

Generated:      Tue Dec  4 12:12:01 GMT 2007
Hostname:       lnx0010
CPU:            IBM/S390
CPU:            IBM/S390
Interface:      hsi0
 -speed:        100Mb/s
 -duplex:       Full
 -autoneg:      on
Interface:      hsi1
 -speed:        100Mb/s
 -duplex:       Full
 -autoneg:      on
Interface:      sit0
 -speed:        100Mb/s
 -duplex:       Full
 -autoneg:      on
CPU:            IBM/S390

Generated:      Mon Dec  3 12:34:19 GMT 2007
Hostname:       ptsuse3
CPU:            GenuineIntel
Interface:      eth0
 -speed:        100Mb/s
 -duplex:       Full
 -autoneg:      on
Interface:      eth1
 -speed:        100Mb/s
 -duplex:       Full
 -autoneg:      on

Generated:      Mon Jun 18 15:33:40 BST 2007
Hostname:       icore-71
CPU:            GenuineIntel
CPU:            GenuineIntel
Interface:      eth0
 -speed:        100Mb/s
 -duplex:       Half
 -autoneg:      on
[download]

# /proc/cpuinfo
vendor_id       : IBM/S390
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