/ 
Log-Handler-0.06
River stage two • 30 direct dependents • 42 total dependents
/ Log::Handler

NAME

Log::Handler - A simple handler to log messages to log files.

SYNOPSIS

use Log::Handler;

my $log = Log::Handler->new( filename => $logfile, mode => 'append' );

$log->alert("foo bar");

DESCRIPTION

This module is just a simple log file handler. It's possible to define a log level for your programs and control the amount of informations that be logged to the log file. In addition it's possible to define how you wish to open the log file, transient or permanent and if you wish you can assign the handler to check the inode of the log file. This could be very useful if a rotate mechanism moves and zip the log file.

METHODS

new()

Call new() to create a new log file object.

The new() method expected the options for the log file. The only one mandatory option is filename. All other options be set to a default value.

Log levels

There are eigth log level and twelve methods to handle this levels:

debug()
info()
notice(), note()
warning()
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(), 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 all methods is very simple:

$log->info("Hello World! How are you?");

Or maybe:

$log->info("Hello World!", "How are you?");

Both calls would log (provided that the log level INFO would log)

Feb 01 12:56:31 [INFO] Hello World! How are you?

would_log_* methods

would_log_debug()
would_log_info()
would_log_notice(), would_log_note()
would_log_warning()
would_log_error(), would_log_err()
would_log_critical(), would_log_crit()
would_log_alert()
would_log_emergency(), would_log_emerg()

This twelve methods could be very useful if you want to kwow if the current log level would log the message to the log file. All methods returns TRUE if the handler would log the message and FALSE if not. Example:

You want to dump a big hash with Data::Dumper to the log file, but you don't want to pass the dump in any case, because it would costs a lot of resources.

$log->debug(Dumper($hash));

This example would dump the $hash in any case and handoff it to the log handler, but this isn't what we really want!

$log->debug(Dumper($hash))
   if $log->would_log_debug();

Now we dump the $hash only if the current log level would really log it.

The methods would_log_note(), would_log_err(), would_log_crit() and would_log_emerg() are just shortcuts.

errstr()

Call errstr() if you want to get the last error string. This is useful with the option die_on_errors. If you set this option to 0 the handler wouldn't croak on errors. Set die_on_errors to control it yourself.

$log->info("log information") or die $log->errstr;

Or

$error_string = $log->errstr
   unless $log->info("log some informations");

The error string contains $! in parantheses at the end of the error string.

The exception is that the handler croaks in any case if the call of new() failed because on missing params or on wrong settings!

my $log = Log::Handler->new(filename => 'file.log', mode => 'foo bar');

This would croaks, because option mode except append or trunc or excl.

If you set the option fileopen to 1 to open the log file permanent and the call of new failed then you can absorb the error.

my $log = Log::Handler->new(filename => 'file.log')
   or warn Log::Handler->errstr;

CLOSE()

Call CLOSE() if you want to close the log file.

This option is only useful if you set option fileopen to 1.

Note that if you close the log file it's necessary to call new() to reopen it.

OPTIONS

filename

The logfile name. This is the only one mandatory option and the script croak if it not set.

filelock

It's maybe desirable to lock the log file by each write operation. 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 log message

fileopen

Open a log file transient or permanent.

0 - open and close the logfile by each write operation (default)
1 - open the logfile if C<new()> called and try to reopen the
    file if reopen is set to 1 and the inode of the file has changed

reopen

This option works only if option fileopen is set to 1.

0 - deactivate
1 - try to reopen logfile if the inode changed (default)

mode

There are thress 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 to open the log file if the log file already exists. If the log file doesn't exist it will be created.

trunc would truncate the complete log file if it exist. Please take care to use this option!

Take a look to the documentation of sysopen() to get more informations and take care to use append or trunc!

autoflush

0 - autoflush off
1 - autoflush on (default)

permissions

permissions sets the permission of the file if it creates and must be set as a octal value. These permission values need to be in octal and are modified by your process's current "umask".

This 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 not exist.

0 - deactivated (default)
1 - 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");

than 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 the options maxlevel and minlevel you can set the log levels you wish to log to your log file. The log levels are:

0 - debug
1 - info
2 - notice, note
3 - warning
4 - error, err
5 - critical, crit
6 - alert
7 - 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 3 and the default minlevel is 7.

Example: If maxlevel is set to 4 and minlevel to 7 then only emergency (emerg), alert, critical (crit) and error (err) messages will be logged to the logfile.

You can set both to 8 if you don't want to log any message.

die_on_errors

Set die_on_errors to 0 if you don't want that the handler croaks if normal operations failed.

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() failed because on missing params or wrong settings.

EXAMPLES

Simple example to log all level:

use Log::Handler;

my $log = Log::Handler->new(
   filename => 'file1.log',
   mode     => 'append',
   newline  => 1,
   maxlevel => 0,
   minlevel => 7
);

$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->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 this:

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 [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   => 2,
   minlevel   => 2,
   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 => 1,
   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!

would_log_* example:

use Log::Handler;
use Data::Dumper;

my $log = Log::Handler->new(
   filename   => 'file1.log',
   mode       => 'trunc',
   maxlevel   => 3,
   prefix     => '',
   timeformat => ''
);

my %hash = (
    foo => 1,
    bar => 2
);

$log->debug("\n".Dumper(\%hash))
    if $log->would_log_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->would_log_debug()) {
   $log->debug("\n".Dumper(\%hash))
      or die $log->errstr();
}

DEPENDENCIES

strict            -  to restrict unsafe constructs
warnings          -  to control optional warnings
Fcntl             -  for flock(), O_APPEND, O_WRONLY, O_EXCL and O_CREATE
IO::Handle        -  to set autoflush on the log file handle
File::stat        -  to get the inode from the log file
POSIX             -  to generate the time stamp with strftime()
Params::Validate  -  to validate all options
Carp              -  to croak() on errors if die_on_errors is active

EXPORTS

No exports.

REPORT BUGS

Please report all bugs to <jschulz.cpan(at)bloonix.de>.

AUTHOR

Jonny Schulz <jschulz.cpan(at)bloonix.de>.

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. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.