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fast logging showing calling position..

by kosun (Acolyte)
on Sep 01, 2005 at 17:34 UTC ( #488436=perlquestion: print w/ replies, xml ) Need Help??
kosun has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I'm want some very simple logging that given something like

file.pl 20: log_error( "a error msg", $level )
prints the equivalent of doing this on the same line
print STDERR "a error msg:" . __FILE__ . __LINE__ if $level >= THRESHOLD;
i.e. It prints the line number where the function was called, not the line number from inside the log_error subrountine.

Stuck on how to do this

1. Printing the line number where the log_error was called without including it in the argument

2. I'd like anything < THRESHOLD for the current run to be removed at compile time if possible to avoid a performance hit...not sure if can really do that...or if it makes a difference.

This application has to be very fast I don't need much and prefer to not use any log modules if I don't need to.

Any help appreciated thanks so much!

Kosun

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Re: fast logging showing calling position..
by ikegami (Pope) on Sep 01, 2005 at 17:51 UTC
    1. Printing the line number where the log_error was called without including it in the argument

    The four Carp routines and the two Carp::Heavy routines provide this info (using caller).

    use Carp (); sub log_error { goto(&Carp::carp) if pop(@_) >= THRESHOLD; }

    I think Log::Log4perl also prints the file name and the line number. The above and Log::Log4perl don't meet your second requirement, however.

     

    2. I'd like anything < THRESHOLD for the current run to be removed at compile time if possible to avoid a performance hit...not sure if can really do that...or if it makes a difference.

    That's not possible if the level is passed as an argument. Your syntax would have to be

    sub DEBUG () { 0 } sub FATAL () { 4 } sub THRESHOLD () { 0 } log_error($msg) if FATAL >= THRESHOLD;

    Well, either that or use a source filter.

     

    Maybe you could compile out debug messages, but leave the other ones in?

    use Carp (); sub WARN () { 1 } sub ERROR () { 2 } sub DEBUG () { 0 } # True of false. sub THRESHOLD () { ERROR } # Or use $THRESHOLD. No real diff. sub log_error { my $level = (@_==2 ? pop(@_) : THRESHOLD); return if $level < THRESHOLD; goto &Carp::carp; } log_error($msg) if DEBUG; # Whole statement removed at compile time. log_error($msg, WARN); # Calls log_error, but not carp. log_error($msg, FATAL); # Calls log_error and carp.
Re: fast logging showing calling position..
by talexb (Canon) on Sep 01, 2005 at 19:20 UTC

    I can highly recommend Log::Log4perl. It matches your requirements very closely. I use it daily and it's terrific.

    Alex / talexb / Toronto

    "Groklaw is the open-source mentality applied to legal research" ~ Linus Torvalds

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