Perl logger example, using a perl module

example.pl

#!/usr/bin/perl

use strict;
use warnings;
use Log;

# Autoflush
$| = 1;

# Usage check
if (@ARGV != 1) {
    print "Use: $0 <logname>\n";
    exit;
}

# Get the logfile
my $LOG_FILE = $ARGV[0];

# Try to open the logfile
(my $res, $_) = Log->start($LOG_FILE);
if ($res) {
    print "Error creating log file: $_\n";
}

# Print some stuff
for my $i (1..10){
    Log->trace("Msg $i")
}

Log.pm

package Log;

my $filename = '';

sub start {
    shift @_;
    ($filename) = @_;
    return (-1, "Filename missing") if (!$filename);

    open (F_LOG, ">>$filename") || return (-1, "Error in file $filename: $!");
    my $fh = select F_LOG;
    # Autoflush
    # http://stackoverflow.com/questions/8804220/perl-operator-dollar-sign-pipe-plus-plus
    $| = 1;
    select $fh;
    return 0;
}

sub trace {
    shift @_;
    my $text = shift @_;
    
    @_ = localtime(time);
    # http://perldoc.perl.org/functions/localtime.html
    $_[5] += 1900;
    $_[4]++;
    my $trace = sprintf "[%02d/%02d/%d %02d:%02d:%02d] %s\n", $_[3], $_[4], $_[5], $_[2], $_[1], $_[0], $text;
    
    print F_LOG $trace;
    print $trace;
    return 0;
}

END {
    close F_LOG;
}

# Modules have to return a True value
1;