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Extract if pattern matches


 
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# 8  
Old 10-20-2007
I am bad at explaining, please read the man page of awk for the definition of FNR and NR
Quote:
FNR The input record number in the current input file.
NR The total number of input records seen so far.
so FNR==NR roughly means going over the first file's records...using 2 input files is a way to get back to the beginning of a file (unless there's another way) because awk process records in the forward direction.
# 9  
Old 10-20-2007
Hi GhostDog,

Thanks for your explanation. But still it seems abstract to me.

Can i say that this statement " FNR==NR&&/^\*\*/{line=$2;next} " will only operate on the 1st input file since the rest of the code is un-true for the 1st input file ?

As for the next part of the code starting with " FNR!=NR&&$0~line .... " , it will only operate on the 2nd input file ?

Am i understanding it correctly ?

But what would be the value of FNR and NR values when operating on the 1st input file ?
And what would be the value of FNR and NR values when operating on the 2nd input file ?
# 10  
Old 10-20-2007
it very easy if you want to try to understand,just print them out !
Code:
awk 'FNR==NR{print "File processing now: " FILENAME "  FNR: "FNR " NR: "NR ;print $0;next}
     { print "File processing now: " FILENAME " NR: " NR " FNR:  " FNR " : "$0 }
' "file1" "file2"

# 11  
Old 10-20-2007
Quote:
Originally Posted by ghostdog74
it very easy if you want to try to understand,just print them out !
Code:
awk 'FNR==NR{print "File processing now: " FILENAME "  FNR: "FNR " NR: "NR ;print $0;next}
     { print "File processing now: " FILENAME " NR: " NR " FNR:  " FNR " : "$0 }
' "file1" "file2"


Hi GhostDog,

Thanks for that!!!! It really helps me to understand the codes better. Smilie
# 12  
Old 10-22-2007
awk

Hi,

I think this one should be ok for you!

code:
Code:
awk 'BEGIN{flag=0}
{
if ($2=="XXX")
{
	print
	flag=1
}
if ($1=="**" && $2!="XXX")
	flag=0
if (flag==1 && $2=="k=")
	print
}' filename

# 13  
Old 10-22-2007
Hi Summer,

Thanks for your code. But we do not know the value of 2nd field (which is XXX) in the 1st place so your code can't apply here.

Hi GhostDog,

I have a little problem here. I have added some more data to my input file (highlighted in blue).
If the 2nd field of last occurence of last occurence of this pattern " ** abc ccc cc cc cc cc 2007 " does not start with " XX ", then the below will be output (that is only the very last portion of the block which matches the pattern will be printed out)

Can you help ?

Input:

wwwwww
0999 k= 1
wwwwww
** XXX ccc ccc cc cc ccc 2007
wwwwww
wwwwww
0001 k= 1
wwwwww
0002 k= 1
** abc ccc cc cc cc cc 2007
wwwwww
0001 k= 1
wwwwww
0002 k= 1
wwwwww
wwwwww
0003 k= 1
wwwwww
** XXX ccc ccc cc cc ccc 2007
wwwwww
0003 k= 1
wwwwww
0004 k= 1
0005 k= 1
** abc ccc cc cc cc cc 2007
0001 k= 1
wwwwww
0002 k= 1
0003 k= 1


Output:

** abc ccc cc cc cc cc 2007
0001 k= 1
0002 k= 1
0003 k= 1
# 14  
Old 10-22-2007
Hi, Raynon.

Thanks for your emphasis on the function of your notation "XXX". Here is an amended perl script to account for that:
Code:
#!/usr/bin/perl

# @(#) p3       Demonstrate extraction after pattern match.

use warnings;
use strict;

my ($debug);
$debug = 1;
$debug = 0;

our ($lines) = 0;
my ($key_string);

my (@a);

# Get second field of first line that begins with **, as in:
#
# ** XXX
#
# then use that second field as the key_string. Anytime that
# key_string appears, we begin scanning for "k=" lines, and only
# stopping when another "**" line appears.
#
# So, read until ** XXX, then turn over control to function to
# scan for other pattern.

my ($first) = 1;
while (<>) {
  if ($first) {
    @a = split;
    if ( $a[0] eq "**" ) {
      $key_string = $a[1];
      $first      = 0;
      redo;
    }
  }
  $lines++;
  chomp;
  @a = split;
  if ( $a[0] eq "**" && $a[1] eq $key_string ) {
    print " Found XXX line at $.\n" if $debug;
    print "$_\n";

    # last if not extract_k();
    $_ = extract_k();
    if ( not $_ ) {
      last;
    }
    else {
      print " cycling with line $. ", $_ if $debug;

      # Adjust line count to avoid counting twice.
      $lines--;
      redo;
    }
  }
}

print STDERR " ( Lines read: $lines )\n";

# Extract k= lines until line with "**".

sub extract_k {
  our ($lines);
  my (@a);
  while (<>) {
    $lines++;
    chomp();
    @a = split;
    return "$_\n" if $a[0] eq "**";    # not EOF
    print "$_\n" if /k=/;
  }
  return 0;                            # EOF
}

exit(0);

Running on the new data in file data3:
Code:
% ./p3 data3
** XXX ccc ccc cc cc ccc 2007
0001 k= 1
0002 k= 1
** XXX ccc ccc cc cc ccc 2007
0003 k= 1
0004 k= 1
0005 k= 1
 ( Lines read: 29 )

cheers, drl

( edit 1: corrected line count )

Last edited by drl; 10-22-2007 at 02:39 AM..

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