Anything awk/grep can do perl can do better! You don't need to inefficiently call them externally, perl already has adopted their strengths.

sub get_log_data {
    open my $logfile, '<', 'logfile' or die "open on logfile: $!";
    my @data_lines;
    while (<$logfile>) {
        next unless ( /fileid/ .. /^-{5}/ ); # range operator!
        if (/specificdata/) {
            push @data_lines, $_;
        }
    }
    close $logfile;
    die 'could not find specificdata in logfile' unless (@data_lines);
    return join q{}, @data_lines;
}
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Please try to enclose your code and error message in <c> and </c> tags in the future. Your error did not display right and the code is easier to read with these tags.

Update: fixed bug where only one line of specificdata matching would be returned, not multiple lines.

Anything awk/grep can do perl can do better!

Suggesting a 15 line sub as alternative for a short one liner doesn't present anything in support of your claim.

Hi, Thanks, but im very very new to perl. the fileid and the specific data in the code are also stored in an array. i pick them from an array store them in a variable and substitute them in the command. Also i am not familiar with shell scripting.

I would suggest playing with creating subs and passing them arguments if you haven't already. Like this example you can take code you already have and put them in a nice friendly named container. This is a fundamental skill that is very handy.

Call the sub with just the $fileid and $specificdata that you want given as arguments.

You retrieve the arguments very easily:

sub get_log_data
{
    my ($fileid, $match) = @_;
    #...
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Then just replace fileid with $fileid and specificdata with $match.

As you can see there are many other ways to do this. I provided the longest way I could think of because I hoped it would be easier to understand and learn from. Short one-liners generally have many subtle concepts that make them work. i.e. here is the sub using johngg's approach, one I would use for a quick n dirty script.

sub get_log_data
{
    my ($fileid, $match) = @_;
    local @ARGV = 'logfile';
    return join '', grep { (/$fileid/o .. /\A-{5}/) && /$match/o } <>;
}
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I'd suggest using a long, explicit, easy to debug, easy to understand version for a beginner; as a learning exercise.

juster's advice to do the job in Perl is sound and the task need not take many lines of code.

use strict;
use warnings;

my @wantedLines =
   grep { m{^fileid} .. m{^-----} and m{pattern} } <>;

print for @wantedLines;
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Here is a pretend log file.

$ cat spw765108.log 
a line
another line
fileid 123
some data
a pattern we want
some more data
another wanted pattern
yet more data
-----
another line
a pattern outside our bounds
last line
$
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Now run the script, giving the log file as an argument.

$ ./spw765108 spw765108.log 
a pattern we want
another wanted pattern
$
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The <> reads the filehandle automatically opened on the file (or files) supplied as arguments to the script. The built-in grep filters the lines read from the filehandle to pass into @wantedLines only those that satisfy the conditions set. The first condition uses the range operator (also known as the flip-flop operator) to select only those lines between the two conditions. A further test to see if any lines match the desired pattern also has to be true.

I hope this is helpful.

What operating system are you running this perl script on? What shell is being used by that operating system? When I run your command on using backtics on my system (Debian Linux, bash shell) I don't get an error at all.

If you need portability across operating systems, I recommend you stay away from backtics and pipes and instead use Perl functions. The following short script does the same thing as your grep/awk combination:

#strictures - put these two lines at the top of every Perl script
#these do a lot of the debugging work for you
use strict;
use warnings;

... lots of other stuff ...

# do: awk '/fileid/,/^-----/' logfile | grep specificdata
my $bPrint=0;
open LOGFILE, '<', "Monks/tmp/logfile.txt" or die;
while (my $line = <LOGFILE>) {

  #equivalent to awk '/fileid/,/^-----/' logfile
  $bPrint = 1 if $line =~ /fileid/;
  $bPrint = 0 if $bPrint && $line =~ /^-----/;

  #equivalent to grep specific data
  print $line if $bPrint && $line =~ /specificData/;
}
close LOGFILE;
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To learn more about the Perl concepts involved in the above code:

• strict and warnings explain what the two lines at the beginning mean and what they can do for you
• perlopentut - will explain how to open and close files in Perl
• retut - will explain how to use =~ to filter data using regular expressions. Perl regular expressions are much more powerful than the awk regular expressions with which you are probably familiar.
• perlport - things to watch out for if you are using Perl on multiple operating system to other.

Best, beth

A coupla things:

• The error message appears to be AIX in origin ... and I'm not able to reproduce your problem on AIX 5.3.
• In this case, there's no need to use both awk and grep, one or the other will do.

awk '/fileid/,/^-----/ { /specificdata/ { print } }' logfile
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