NAME Log::Handler - A simple handler to log messages to a log file. SYNOPSIS use Log::Handler; my $log = Log::Handler->new(); $log->alert("foo bar"); DESCRIPTION This module is just a simple object oriented log file handler and very easy to use. It's possible to define a log level for your programs and control the amount of informations that will be logged to the log file. In addition it's possible to configure how you wish to open the log file - transient or permanent - and lock and unlock the log file by each write operation. If you wish you can assign the handler to check the inode of the log file (not on Windows). That could be very useful if a rotate mechanism moves and zip the log file. METHODS new() Call "new()" to create a new log handler object. The "new()" method expected the options for the log file. Each option will be set to a default value if not set. Log levels There are eigth log levels and thirteen methods to handle this levels: debug() info() notice(), note() warning(), warn() error(), err() critical(), crit() alert() emergency(), emerg() "debug()" is the highest and "emergency()" or "emerg()" is the lowest log level. You can define the log level with the options "maxlevel" and "minlevel". The methods "note()", "warn()", "err()", "crit()" and "emerg()" are just shortcuts. Example: If you set the option "maxlevel" to "warning" and "minlevel" to "emergency" then the levels emergency, alert, critical, error and warning will be logged. The call of a log level method is very simple: $log->info("Hello World! How are you?"); Or maybe: $log->info("Hello World!", "How are you?"); Both calls write to the log file (provided that the log level INFO would log) Feb 01 12:56:31 [INFO] Hello World! How are you? is_* methods is_debug() is_info() is_notice(), is_note() is_warning(), is_warn() is_error(), is_err() is_critical(), is_crit() is_alert() is_emergency(), is_emerg() These thirteen methods could be very useful if you want to kwow if the current log level would write the message to the log file. All methods returns TRUE if the handler would log it and FALSE if not. Example: $log->debug(Dumper(\%hash)); This example would dump the hash in any case and handoff it to the log handler, but this isn't that what we really want because it could costs a lot of resources. $log->debug(Dumper(\%hash)) if $log->is_debug(); Now we dump the hash only if the current log level would log it. The methods "is_note()", "is_warn()", "is_err()", "is_crit()" and "is_emerg()" are just shortcuts. set_prefix() Call "set_prefix()" to modifier the option prefix after you called "new()". my $log = Log::Handler->new( filename => 'file.log', mode => 'append', prefix => "myhost:$$ [<--LEVEL-->] " ); $log->set_prefix("[<--LEVEL-->] myhost:$$ "); get_prefix() Call "get_prefix()" to get the current prefix if you want to modifier it. # safe the old prefix my $old_prefix = $log->get_prefix(); # set a new one for a code part in your script $log->set_prefix("my new prefix"); # now set the your old prefix again $log->set_prefix($old_prefix); Or you want to add something to the current prefix: $log->set_prefix($log->get_prefix."add something"); errstr() Call "errstr()" if you want to get the last error message. That is useful with "die_on_errors". If you set this option to 0 then the handler wouldn't croak if a simple write operation fails. Set "die_on_errors" to control it yourself. "errstr()" is only useful with "new()", "close()" and the log level methods. $log->info("Hello World!") or die $log->errstr; Or $error_string = $log->errstr unless $log->info("Hello World!"); The exception is that the handler croaks in any case if the call of "new()" fails because on missing params or wrong settings! my $log = Log::Handler->new(filename => 'file.log', mode => 'foo bar'); That would croak, because the option "mode" except "append" or "trunc" or "excl". If you set the option "fileopen" to 1 - the default - to open the log file permanent and the call of "new" fails then you can absorb the error. my $log = Log::Handler->new( filename => 'file.log', die_on_errors => 0 ) or warn Log::Handler->errstr; close() Call "close()" if you want to close the log file. This option is only useful if you set the option "fileopen" to 1 and if you want to close the log file yourself. If you don't call "close()" the log file will be closed automatically before exit. trace() This method is very useful if you want to print "caller()" informations to the log file. In contrast to the log level methods this method prints "caller()" informations to the log file in any case and you don't need to activate the debugger with the option "debug". Example: my $log = Log::Handler->new( filename => \*STDOUT ); $log->trace("caller informations:"); Jun 05 21:20:32 [TRACE] caller informations CALL(2): package(main) filename(./log-handler-test.pl) line(22) subroutine(Log::Handler::trace) hasargs(1) CALL(1): package(Log::Handler) filename(/usr/local/share/perl/5.8.8/Log/Handler.pm) line(941) subroutine(Log::Handler::_print) hasargs(1) CALL(0): package(Log::Handler) filename(/usr/local/share/perl/5.8.8/Log/Handler.pm) line(1097) subroutine(Devel::Backtrace::new) hasargs(1) wantarray(0) Maybe you like to print caller informations to the log file if an unexpected error occurs. $SIG{__DIE__} = sub { $log->trace(@_) }; Take a look at the examples of the options "debug", "debug_mode" and "debug_skip" for more informations. OPTIONS filename With "filename" you can set a file name, a GLOBREF or you can set a string as an alias for STDOUT or STDERR. The default is STDOUT for this option. Set a file name: my $log = Log::Handler->new( filename => 'file.log' ); Set a GLOBREF open FH, '>', 'file.log' or die $!; my $log = Log::Handler->new( filename => \*FH ); Or the same with open my $fh, '>', 'file.log' or die $!; my $log = Log::Handler->new( filename => $fh ); Set STDOUT or STDERR my $log = Log::Handler->new( filename => \*STDOUT ); # or my $log = Log::Handler->new( filename => \*STDERR ); If the option "filename" is set in a config file and you want to debug to your screen then you can set *STDOUT or *STDERR as a string. my $log = Log::Handler->new( filename => '*STDOUT' ); # or my $log = Log::Handler->new( filename => '*STDERR' ); That is not possible: my $log = Log::Handler->new( filename => '*FH' ); Note that if you set a GLOBREF to "filename" some options will be forced (overwritten) and you have to control the handles yourself. The forced options are fileopen => 1 filelock => 0 reopen => 0 filelock Maybe it's desirable to lock the log file by each write operation because a lot of processes write at the same time to the log file. You can set the option "filelock" to activate or deactivate the locking. 0 - no file lock 1 - exclusive lock (LOCK_EX) and unlock (LOCK_UN) by each write operation (default) fileopen Open a log file transient or permanent. 0 - open and close the logfile by each write operation 1 - open the logfile if C called and try to reopen the file if C is set to 1 and the inode of the file has changed (default) reopen This option works only if option "fileopen" is set to 1. 0 - deactivate 1 - try to reopen the log file if the inode changed (default) fileopen and reopen Please note that it's better to set "reopen" and "fileopen" to 0 on Windows because Windows unfortunately haven't the faintest idea of inodes. To write your code independent you should control it: my $os_is_win = $^O =~ /win/i ? 0 : 1; my $log = Log::Handler->new( filename => 'file.log', mode => 'append', fileopen => $os_is_win ); If you set "fileopen" to 0 then it implies that "reopen" has no importance. mode There are three possible modes to open a log file. append - O_WRONLY | O_APPEND | O_CREAT excl - O_WRONLY | O_EXCL | O_CREAT (default) trunc - O_WRONLY | O_TRUNC | O_CREAT "append" would open the log file in any case and appends the messages at the end of the log file. "excl" would fail by open the log file if the log file already exists. This is the default option because some security reasons. "trunc" would truncate the complete log file if it exists. Please take care to use this option. Take a look to the documentation of "sysopen()" to get more informations. autoflush 0 - autoflush off 1 - autoflush on (default) permissions The option "permissions" sets the permission of the file if it creates and must be set as a octal value. The permission need to be in octal and are modified by your process's current "umask". That means that you have to use the unix style permissions such as "chmod". 0640 is the default permission for this option. That means that the owner got read and write permissions and users in the same group got only read permissions. All other users got no access. Take a look to the documentation of "sysopen()" to get more informations. timeformat You can set "timeformat" with a date and time format that will be coverted by POSIX::strftime. The default format is "%b %d %H:%M:%S" and looks like Feb 01 12:56:31 As example the format "%Y/%m/%d %H:%M:%S" would looks like 2007/02/01 12:56:31 newline This helpful option appends a newline to the log message if it not exist. 0 - inactive (default) 1 - active - appends a newline to the log message if not exist prefix Set "prefix" to define your own prefix for each message. The default value is "[<--LEVEL-->] ". "<--LEVEL-->" is replaced with the current message level. Default example: $log->alert("message ..."); would log Feb 01 12:56:31 [ALERT] message ... If you set "prefix" to prefix => 'foo <--LEVEL--> bar: ' $log->info("foobar"); then it would log Feb 01 12:56:31 foo INFO bar: foobar Take a look to the EXAMPLES to see more. maxlevel and minlevel With these options it's possible to set the log levels for your program. The log levels are: 7 - debug 6 - info 5 - notice, note 4 - warning, warn 3 - error, err 2 - critical, crit 1 - alert 0 - emergency, emerg The levels "note", "err", "crit" and "emerg" are just shortcuts. It's possible to set the log level as a string or as number. The default "maxlevel" is 4 and the default "minlevel" is 0. Example: If "maxlevel" is set to 4 and "minlevel" to 0 then the levels emergency (emerg), alert, critical (crit) and error (err) are active and would be logged to the log file. You can set both to 8 or "nothing" if you don't want to log any message. rewrite_to_stderr Set this option to 1 if you want that Log::Handler prints messages to STDERR if the message couldn't print to the log file. The default is 0. die_on_errors Set "die_on_errors" to 0 if you don't want that the handler croaks if normal operations fail. 0 - will not die on errors 1 - will die (e.g. croak) on errors The exception is that the handler croaks in any case if the call of "new()" fails because on missing params or wrong settings. utf8 If this option is set to 1 then UTF-8 will be set with "binmode()" on the output filehandle. debug You can activate a simple debugger that writes "caller()" informations for each log level that would log to the log file. The debugger is logging all defined values except "hints" and "bitmask". Set "debug" to 1 to activate the debugger. The debugger is set to 0 by default. debug_mode There are two debug modes: line(1) and block(2) mode. The default mode is 1. The block mode looks like this: use strict; use warnings; use Log::Handler; my $log = Log::Handler->new( maxlevel => 'debug', debug => 1, debug_mode => 1 ); sub test1 { $log->debug() } sub test2 { &test1; } &test2; Output: Apr 26 12:54:11 [DEBUG] CALL(4): package(main) filename(./trace.pl) line(15) subroutine(main::test2) hasargs(0) CALL(3): package(main) filename(./trace.pl) line(13) subroutine(main::test1) hasargs(0) CALL(2): package(main) filename(./trace.pl) line(12) subroutine(Log::Handler::__ANON__) hasargs(1) CALL(1): package(Log::Handler) filename(/usr/local/share/perl/5.8.8/Log/Handler.pm) line(713) subroutine(Log::Handler::_print) hasargs(1) CALL(0): package(Log::Handler) filename(/usr/local/share/perl/5.8.8/Log/Handler.pm) line(1022) subroutine(Devel::Backtrace::new) hasargs(1) wantarray(0) The same code example but the debugger in block mode would looks like this: debug_mode => 2 Output: Apr 26 12:52:17 [DEBUG] CALL(4): package main filename ./trace.pl line 15 subroutine main::test2 hasargs 0 CALL(3): package main filename ./trace.pl line 13 subroutine main::test1 hasargs 0 CALL(2): package main filename ./trace.pl line 12 subroutine Log::Handler::__ANON__ hasargs 1 CALL(1): package Log::Handler filename /usr/local/share/perl/5.8.8/Log/Handler.pm line 681 subroutine Log::Handler::_print hasargs 1 CALL(0): package Log::Handler filename /usr/local/share/perl/5.8.8/Log/Handler.pm line 990 subroutine Devel::Backtrace::new hasargs 1 wantarray 0 debug_skip This option let skip the caller informations the count of "debug_skip". debug_skip => 2 Apr 26 12:55:07 [DEBUG] CALL(2): package(main) filename(./trace.pl) line(16) subroutine(main::test2) hasargs(0) CALL(1): package(main) filename(./trace.pl) line(14) subroutine(main::test1) hasargs(0) CALL(0): package(main) filename(./trace.pl) line(13) subroutine(Log::Handler::__ANON__) hasargs(1) EXAMPLES Simple example to log all level: use Log::Handler; my $log = Log::Handler->new( filename => 'file1.log', mode => 'append', newline => 1, maxlevel => 7, minlevel => 0 ); $log->debug("this is a debug message"); $log->info("this is a info message"); $log->notice("this is a notice"); $log->note("this is a notice as well"); $log->warning("this is a warning"); $log->warn("this is a warning as well"); $log->error("this is a error message"); $log->err("this is a error message as well"); $log->critical("this is a critical message"); $log->crit("this is a critical message as well"); $log->alert("this is a alert message"); $log->emergency("this is a emergency message"); $log->emerg("this is a emergency message as well"); Would log Feb 01 12:56:31 [DEBUG] this is a debug message Feb 01 12:56:31 [INFO] this is a info message Feb 01 12:56:31 [NOTICE] this is a notice Feb 01 12:56:31 [NOTE] this is a notice as well Feb 01 12:56:31 [WARNING] this is a warning Feb 01 12:56:31 [WARN] this is a warning Feb 01 12:56:31 [ERROR] this is a error message Feb 01 12:56:31 [ERR] this is a error message as well Feb 01 12:56:31 [CRITICAL] this is a critical message Feb 01 12:56:31 [CRIT] this is a critial message as well Feb 01 12:56:31 [ALERT] this is a alert message Feb 01 12:56:31 [EMERGENCY] this is a emergency message Feb 01 12:56:31 [EMERG] this is a emergency message as well Just a notice: use Log::Handler; my $log = Log::Handler->new( filename => '/var/run/pid-file1', mode => 'trunc', maxlevel => 5, minlevel => 5, prefix => '', timeformat => '' ); $log->note("$$"); Would truncate /var/run/pid-file1 and write just the pid to the logfile. Selfmade prefix: use Log::Handler; use Sys::Hostname; my $hostname = hostname; my $pid = $$; my $progname = $0; $progname =~ s@.*[/\\]@@; my $log = Log::Handler->new( filename => "${progname}.log", mode => 'append', maxlevel => 6, newline => 1, prefix => "${hostname}[$pid] [<--LEVEL-->] $progname: " ); $log->info("Hello World!"); $log->warning("There is something wrong!"); Would log: Feb 01 12:56:31 hostname[8923] [INFO] progname: Hello world Feb 01 12:56:31 hostname[8923] [WARNING] progname: There is something wrong! is_* example: use Log::Handler; use Data::Dumper; my $log = Log::Handler->new( filename => 'file1.log', mode => 'append', maxlevel => 4, ); my %hash = (foo => 1, bar => 2); $log->debug("\n".Dumper(\%hash)) if $log->is_debug(); Would NOT dump %hash to the $log object! die_on_errors example: use Log::Handler; use Data::Dumper; my $log = Log::Handler->new( filename => 'file1.log', mode => 'append', die_on_errors => 0 ) or die Log::Handler->errstr(); if ($log->is_debug()) { $log->debug("\n".Dumper(\%hash)) or die $log->errstr(); } PREREQUISITES Fcntl - for flock(), O_APPEND, O_WRONLY, O_EXCL and O_CREATE POSIX - to generate the time stamp with strftime() Params::Validate - to validate all options Devel::Backtrace - to backtrace caller() Carp - to croak() on errors if die_on_errors is active EXPORTS No exports. REPORT BUGS Please report all bugs to . AUTHOR Jonny Schulz . QUESTIONS Do you have any questions or ideas? MAIL: IRC: irc.perl.org#perlde If you send me a mail then add Log::Handler into the subject. COPYRIGHT Copyright (C) 2007 by Jonny Schulz. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. DISCLAIMER OF WARRANTY BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. 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