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How to determine current line executing in Script

by bearslumber (Novice)
on Dec 04, 2008 at 12:08 UTC ( #727944=perlquestion: print w/ replies, xml ) Need Help??
bearslumber has asked for the wisdom of the Perl Monks concerning the following question:

Hallo Monks,

I am trying to find a way to dynamically determine the current line being executed in my script.

I have a batch script which I accumulate a progress report or log whilst it is running and then output the log to a file on completion. I wish to add the current line number being executed in the script to each instance in the report

The following describes a snippet of code to demonstrate my requirement. I have annotated the code with line numbers for demonstration purposes

1. #!/usr/bin/perl 2. use warnings; 3. use strict; 4. 5. my @log ; 6. . . . 25. my $success = &Get_Item_From_File ($file) 26. 27. if ($Success) { 28. $_ref_DB_DD_OSD = &Get_DB_OSD ($_ref_Model) 29. } 30. else { 31. push (@log, "Read $file not successfull" . "31") ; 32. } . . . 1024 print <FILE> @log ; 1025 exit ; .

The following demonstrates the hard coded method at line 31, but if there is a way of determining this dynamically then this would reduce the need to have to manually update the hard coded value whenever the script is modified.

I envisage substituting line 31 as follows:

 push (@log, "Read $file not successfull" . &function_returning_current_line) ;

or anything similar; i.e. Get a near enough line number before the call to push etc

Any help would be greatly appreciated

Best regards

Lucas Redding AKA Bearslumber

Comment on How to determine current line executing in Script
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Re: How to determine current line executing in Script
by ccn (Vicar) on Dec 04, 2008 at 12:11 UTC

      Hi ccn

      Many thanks for your prompt reply. I blinked and you had already replied.

      I have looked at Log4Perl and having read the POD, it does just the job. i.e. layout = %L.

      Much appreciated.

      Lucas AKA: Bearslumber

Re: How to determine current line executing in Script
by Corion (Pope) on Dec 04, 2008 at 12:14 UTC

    Also see perldata about __LINE__, and possibly caller, should you want to put your logging code into a subroutine.

Re: How to determine current line executing in Script
by clinton (Priest) on Dec 04, 2008 at 12:15 UTC
    You can use __LINE__. See "Special literals" in perldata.
Re: How to determine current line executing in Script
by Anonymous Monk on Dec 04, 2008 at 12:56 UTC
    Make use of warn, $SIG{__WARN__} and END {...}. If the argument to warn doesn't end with a new line ( warn $x." "; ) then the line number will be appended. In $SIG{__WARN__} do a "push(@log,"@_");". In the END block print @log. You probably should add a $SIG{__DIE__} where you also do the "push(@log ..." before you re-raise the die. That way you'll get a log if you "die".
      #!/usr/bin/perl use strict; use warnings; my @log="\n"; BEGIN { $SIG{__WARN__}=sub { push(@log,"@_"); }; $SIG{__DIE__}=sub { push(@log,"@_"); }; } # BEGIN END { if (@log) { print @log; }; } # END warn "a warning "; my $warning="just another warning\n"; warn $warning." "; die "death by request";
Re: How to determine current line executing in Script
by bearslumber (Novice) on Dec 04, 2008 at 13:47 UTC

    All.

    Many thanks for your replies. I am grateful for all responses.

    Here is my conclusion...

    1. Log4Perl: Brilliant package. Does everything I could ever have imagined would be required in a log. I just wish I had known about it when I embarked on this project. I would use this if I was to start again.

    2. Perdata __LINE__: Getting there. A quick solution, seems to be just what I was hoping for.

    3. caller: This is icing on the cake.

    4. Make use of warn, $SIG{__WARN__} and END {...}: And I can now ensure I get the log out regardless of the death of my script.

    I am truly spoilt for choice, and for this project will definately be using caller and will Make use of warn, $SIG{__WARN__} and END {...}:.

    I shall definitley find use for verything sometime in future.

    Many thanks again.

    Lucas Bearslumber

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