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;

    $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<new()> called and try to reopen the
        file if C<reopen> 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 <jschulz.cpan(at)bloonix.de>.

AUTHOR

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

QUESTIONS

Do you have any questions or ideas?

MAIL: <jschulz.cpan(at)bloonix.de>

IRC: irc.perl.org#perlde

If you send me a mail then add Log::Handler into the subject.

COPYRIGHT

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.

To install Log::Handler, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Log::Handler

CPAN shell

perl -MCPAN -e shell
install Log::Handler

For more information on module installation, please visit the detailed CPAN module installation guide.

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