need help with perl

johngreg · 10-13-2008, 02:45 AM

i need to write a script to find the count of traces in the log and generate a report.

trace looks something like this...

Code:

[10/10/08 09:12:25:539 CDT]  SEVERE  00000060  efox1dsKSNHRz7_pf4K2_z3  com..billing.UpdateCard
Correlation Identity: 767718e0-96d5-11dd-8f9a-82e948eef517
Additional Data:
        null
Current exception:
Message:
   _ERR_COMMAND_EXCEPTION
Stack trace:
"java.lang.NullPointerException".
        at com.command.ECCommandTarget.executeCommand(ECCommandTarget.java(Compiled Code))
        at com.command.CommandCache.executeCommand(CommandCache.java(Compiled Code))
.
.
End of exception traces.

Text in between 'Stack trace:' and 'End of exception traces.' is one trace.
I tried the below methods, but dint get expected result.

Code:

my $exStart ="Stack trace";
my $exEnd = "End of exception traces.";
1. if(/$exStart/ ... /$exEnd/){
2. split(/^$exStart.*$exEnd/, <FH>);

the problem is, it is getting the text from first 'Stack trace:' to last 'End of exception traces.'

please help

radoulov · 10-13-2008, 06:44 AM

If I understand correctly:

Code:

perl -nle'
  if (/Stack trace/../End of exception/) {
    /Stack trace/ and ++$c;
    print
    }
  print "Total: $c" if eof' logfile

Telemachos · 10-13-2008, 07:09 AM

Quote:

Originally Posted by johngreg

the problem is, it is getting the text from first 'Stack trace:' to last 'End of exception traces.'

The regular expression engine is greedy by default, meaning it takes as much as it can get. If you say /x.*y/, then you get from 'x' to the last 'y' the engine can find. There's a way to change this behavior, however, by changing '.*' to '.*?'. See perldoc perlretut and look for the description of greedy (maximal) matching vs non-greedy (minimal) matching.

A random example:

Code:

#!/usr/bin/perl
use strict;
use warnings;

while( <DATA> ) {
  m/foo(.*)bar/ and print "Greedy: $1\n";
  m/foo(.*?)bar/ and print "Non-greedy: $1\n";
}

__DATA__
foo 1 2 3 bar foo 4 5 6 bar foo 7 8 9 bar

Which produces this:

Code:

telemachus ~ $ perl greedy 
Greedy:  1 2 3 bar foo 4 5 6 bar foo 7 8 9 
Non-greedy:  1 2 3

johngreg · 10-13-2008, 11:05 AM

i was trying the below way, i couldn't get it to work..

Code:

my @chunks = split(m/^$exStart(.*?)$exEnd/, <FH>);

please help

johngreg · 10-13-2008, 11:36 AM

thanks guys.. i got it working like below

Code:

my $exStart ="Stack trace";
my $exEnd = "End of exception traces.";
my $c;
my @traces;
while(<FH>){
    while ( /$exStart(.*?)$exEnd/sgmo ) {
        ++$c;
        push(@traces, $1);
    }
}

i would appreciate any suggestions to improve this.. thanks again

sundialsvcs · 10-13-2008, 01:08 PM

If the regular-expression that you want to match-for is expressed in terms of Perl variables, then you need to tell Perl to do what's known as interpolation. In other words, to first substitute the variables into the string and then use that result as "the pattern to be matched."

Refer to the section, "Regexp-Like Quote Operators" in perldoc perlop.