in reply to Buffered read and matching

Read the file line for line and use a flag to indicate whether you want to collect lines or not, you could also call it a simple state machine:

my $errormatching=0;
my @errortext='';
while (<>) {
  if (not $errormatching) {
    $errormatching=1 if m{^\s*'Errors' =>};
  }
  else {
    if (not m{^\s*\]}) {
       push @errortext, $_;
    }
    else {
      process_error(@errortext);
      @errortext=();
      $errormatching=0;
    }
  }
}

[download]

UPDATE: Fixed typo where I used [ instead of ] in the regex

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Re^2: Buffered read and matching
by Perlbotics (Archbishop) on Oct 15, 2008 at 12:35 UTC

    Right, I wanted to suggest some state machine along this too: 

    #!/usr/bin/perl

use strict;
my @lines;

sub flush {
        return unless grep(/'Errors'/, @_);
        print "Got:\n\t", join ("\t", @_), "\n";
}

while (<>) {
        # trigger on last line of an error message
        flush(@lines,$_),@lines=(),next if m{^\s*\};\s*$}; 
        # triggger on next timestamp
        flush(@lines),   @lines=()      if m{^\s*\[\d\d\d\d\/};
        push(@lines, $_);
}
flush(@lines);

    [download]
    However, all solutions I have seen so far trigger evaluation with the next timestamp only. When using tail -f, the error will be processed only when the next log-line with a time-stamp is encountered - which might happen some hours or days later. IF seeing an error ASAP is important to the OP, the evaluation should be triggered additionally by matching for }; or by some timeout-mechanism, e.g. using alarm().
    Update: final flush(...) added

[reply]
[d/l]
[select]
      You might have been mislead by a bug in my solution where I used the wrong bracket for end of error detection (which makes the script not work at all), but it does process the error when ] is encountered, i.e. well before the next log-line.
[reply]
[d/l]

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