http://www.perlmonks.org?node_id=295986

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

Friends,

I was just wondering if there is a Perl equivalent to C's __FILE__ and __LINE__ ... you know so I could put annoying 
print "$__FILE__:$__LINE__ stupid debug message!\n";

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statements everywhere.

Thanks

Plankton: 1% Evil, 99% Hot Gas.

Replies are listed 'Best First'.
Re: __FILE__ and __LINE__ for Perl?
by runrig (Abbot) on Oct 02, 2003 at 17:56 UTC
    You'll find __FILE__ and __LINE__ in perldata under Special Literals (along with __PACKAGE__, and the __END__ and __DATA__ tokens), but since they are literals, they are not prefixed with a sigil and are not interpolated inside quotes:
    print "FILE: ", __FILE__, " Line: ", __LINE__, "\n";

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Re: __FILE__ and __LINE__ for Perl?
by dws (Chancellor) on Oct 02, 2003 at 18:00 UTC
    If you're interested in emitting warnings with filenames and line numbers, you might want warn(), which is documented in perlfunc. 
        warn "I'm a warning about something";

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    will produce 
      I'm a warning about something at demo.pl line 47.

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    die() does the same, but stops execution (unless caught in an exception handler).

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      Just to be a little more specific, note that 
      warn "I'm a warning about something";

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      does not contain a trailing newline. If your warning message does contain \n as the last character, warn will not include at demo.pl line 47. See perldoc -f warn

      --
      bm
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Re: __FILE__ and __LINE__ for Perl? (caller)
by tye (Sage) on Oct 02, 2003 at 18:14 UTC

    If dws's suggestion of warn w/o trailing "\n" isn't good enough, you might want to look into using caller to get more control: 

    my $Debugging= ...;
sub Trace {
    return   if  ! $Debugging;
    my( $file, $line )= ( caller )[1,2];
    warn @_, " at $file:$line\n";
}
#...
Trace("stupid debug message");

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                    - tye
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[d/l]
      Why not just use Carp here? croak for die and cluck for warn give you errors from the callers perspective without having to do anythign else. 
      use Carp;

croak "stupid debug message";

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[d/l]
        You mean carp instead of cluck (the latter produces a stack trace as well).

        Makeshifts last the longest.

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Re: __FILE__ and __LINE__ for Perl?
by Zaxo (Archbishop) on Oct 02, 2003 at 19:05 UTC

    Also, you can make __FILE__ and __LINE__ lie with the #line directive (perlsyn), 

    $ perl -e'
> #line 200 "the office"
> warn'
Warning: something's wrong at the office line 200.
$

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    After Compline,
    Zaxo

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