in reply to Re^3: Print line from file only once even if occurrence of pattern is more than once in the line
in thread Print line from file only once even if occurrence of pattern is more than once in the line

Thanks pme. That had just three lines before the occurrence of a pattern. My requirement is something like this: The line could have text such as: "ERROR - Critical error" or "ERROR - <module> threw an error" or "FATAL - Fatal error" or "java.lang.OutOfMemoryError" and I needed 5 lines before the matched line, matched line and 5 lines after the matched line to be printed. Note that the lines could occur immediately after one another and I would like to have output print only once in such cases.
  • Comment on Re^4: Print line from file only once even if occurrence of pattern is more than once in the line

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Re^5: Print line from file only once even if occurrence of pattern is more than once in the line
by Cristoforo (Curate) on Mar 30, 2015 at 02:18 UTC
    Note that the lines could occur immediately after one another and I would like to have output print only once in such cases.

    To avoid this, a solution using vec could work for you.

    The line of code vec($vec, $_, 1) ||= 1 for $lo .. $hi; would assign a 1 to each position. So you wouldn't repeat a line when printing out the results. 

    my @log_lines=<$read_tmp_log>;
my $vec = '';

for my $i (0..$#log_lines) {
    next unless lc($log_lines[$i]) =~ /error|fatal|critical/;
    my $lo = $i - 5 < 0 ? 0 : $i - 5;;
    my $hi = $i + 5 > $#log_lines ? $#log_lines : $i + 5;
    vec($vec, $_, 1) ||= 1 for $lo .. $hi;
}

my $newline_needed = 0;
for my $i (0 .. $#log_lines) {
    if (vec($vec, $i, 1) == 1) {
        print $log_lines[$i];
        $newline_needed ||= 1;    
    }
    else {
        print "\n" if $newline_needed;    
        $newline_needed = 0;
    }
}

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