Exit With Line Number

PerlBear has asked for the wisdom of the Perl Monks concerning the following question:

Fellow Monks --
In a nutshell this is what I would like todo: When I exit normally by issuing the command exit; instead of say, having the following line of code:

print "exit line 382\n"; exit;
[download]

Is there a way perhaps by means of some special variable or other process that can perl can tell me which line the program exited on without hard coding it into a preceding print statement?
I did a little digging in perl documentation for special variables (my first thought), but nothing immediately jumped out at me. I will dig more, however, in the meantime I humbly ask for the wisdom of my fellow monks who are more experienced than I in this matter.
As always, any help/insight that you can provide is greatly appreciated!

Comment on Exit With Line Number Download Code

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Re: Exit With Line Number by Roy Johnson (Monsignor) on May 05, 2005 at 16:05 UTC
The token `__LINE__` will give you what you want. You can use it as your exit status or print it before exiting. `die` will also (by default) tell you what line it exited at, but you exit with an error code. Caution: Contents may have been coded under pressure.	[reply] [d/l] [select]
Re: Exit With Line Number by davido (Cardinal) on May 05, 2005 at 16:09 UTC
Well, there is die, and also the `__LINE__` identifier, or you may consider using the Carp module, for finer handling of error conditions. `__LINE__` is an identifier that always evaluates to the current line number in the script. So "`print __LINE__, "\n";` would print the line number where the print function occurs. I hope this helps. Dave	[reply] [d/l] [select]
Re: Exit With Line Number by inman (Curate) on May 05, 2005 at 16:18 UTC
You can always use die with an optional message if you just want to end the program and report the line number. `#! /usr/bin/perl -w use strict; use warnings; print "The end is nigh!\n"; die "Arrrrrgh!"; __END__ The end is nigh! Arrrrrgh! at C:\Daniel\perl\PerlMonks\death.pl line 8.` [download] This is the usual thing to do if you want to exit following a failed test. E.g. `open FILE, "no_such_file" or die $!;` [download]	[reply] [d/l] [select]
Re: Exit With Line Number by shemp (Deacon) on May 05, 2005 at 17:08 UTC
You can use the built-in function caller() to get this sort of information, and much more. Its great for simple debugging. From perldoc: caller EXPR caller Returns the context of the current subroutine call. In scalar context, returns the caller's package name if there is a caller, that is, if we're in a subroutine or "eval" or "require", and the undefined value otherwise. In list context, returns: `($package, $filename, $line) = caller;` [download] With EXPR, it returns some extra information that the debugger uses to print a stack trace. The value of EXPR indicates how many call frames to go back before the current one. `($package, $filename, $line, $subroutine, $hasargs, $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i) +;` [download]	[reply] [d/l] [select]
Re: Exit With Line Number by thundergnat (Deacon) on May 05, 2005 at 17:27 UTC
My personal favorite way to do this is to use "warn" `warn 'Exit' and exit;` Will produce: Exit at (whatever).pl line (whichever).	[reply] [d/l]
Re^2: Exit With Line Number by revdiablo (Prior) on May 05, 2005 at 18:04 UTC
The only time this would be preferable over die, is when you want to return a specific exit code. Otherside, it's just overly verbose.	[reply]
Re^3: Exit With Line Number by thundergnat (Deacon) on May 05, 2005 at 19:26 UTC
Mostly true, though it's also useful when working with Tk, where a simple die often produces warnings about improper program termination.	[reply]
Re: Exit With Line Number by salva (Canon) on May 05, 2005 at 18:51 UTC
you can also redefine `exit`: `sub wexit (;$) { my $status = shift; my ($package, $fn, $line) = caller; print STDERR "exit status $status at $fn line $line\n"; CORE::exit($status) } *CORE::GLOBAL::exit = \&wexit;` [download] though, I would use this solution only for code I could not change, never for new code!	[reply] [d/l] [select]