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Log::Log4perl::Appender::File - Log to file


    use Log::Log4perl::Appender::File;

    my $app = Log::Log4perl::Appender::File->new(
      filename  => 'file.log',
      mode      => 'append',
      autoflush => 1,
      umask     => 0222,

    $file->log(message => "Log me\n");


This is a simple appender for writing to a file.

The log() method takes a single scalar. If a newline character should terminate the message, it has to be added explicitely.

Upon destruction of the object, the filehandle to access the file is flushed and closed.

If you want to switch over to a different logfile, use the file_switch($newfile) method which will first close the old file handle and then open a one to the new file specified.



Name of the log file.


Messages will be append to the file if $mode is set to the string "append". Will clobber the file if set to "clobber". If it is "pipe", the file will be understood as executable to pipe output to. Default mode is "append".


autoflush, if set to a true value, triggers flushing the data out to the file on every call to log(). autoflush is on by default.


syswrite, if set to a true value, makes sure that the appender uses syswrite() instead of print() to log the message. syswrite() usually maps to the operating system's write() function and makes sure that no other process writes to the same log file while write() is busy. Might safe you from having to use other syncronisation measures like semaphores (see: Synchronized appender).


Specifies the umask to use when creating the file, determining the file's permission settings. If set to 0222 (default), new files will be created with rw-r--r-- permissions. If set to 0000, new files will be created with rw-rw-rw- permissions.


If set, specifies that the owner of the newly created log file should be different from the effective user id of the running process. Only makes sense if the process is running as root. Both numerical user ids and user names are acceptable. Log4perl does not attempt to change the ownership of existing files.


If set, specifies that the group of the newly created log file should be different from the effective group id of the running process. Only makes sense if the process is running as root. Both numerical group ids and group names are acceptable. Log4perl does not attempt to change the group membership of existing files.


If you're printing out Unicode strings, the output filehandle needs to be set into :utf8 mode:

    my $app = Log::Log4perl::Appender::File->new(
      filename  => 'file.log',
      mode      => 'append',
      utf8      => 1,

To manipulate the output filehandle via binmode(), use the binmode parameter:

    my $app = Log::Log4perl::Appender::File->new(
      filename  => 'file.log',
      mode      => 'append',
      binmode   => ":utf8",

A setting of ":utf8" for binmode is equivalent to specifying the utf8 option (see above).


Normally, if a file appender logs to a file and the file gets moved to a different location (e.g. via mv), the appender's open file handle will automatically follow the file to the new location.

This may be undesirable. When using an external logfile rotator, for example, the appender should create a new file under the old name and start logging into it. If the recreate option is set to a true value, Log::Log4perl::Appender::File will do exactly that. It defaults to false. Check the recreate_check_interval option for performance optimizations with this feature.


In recreate mode, the appender has to continuously check if the file it is logging to is still in the same location. This check is fairly expensive, since it has to call stat on the file name and figure out if its inode has changed. Doing this with every call to log can be prohibitively expensive. Setting it to a positive integer value N will only check the file every N seconds. It defaults to 30.

This obviously means that the appender will continue writing to a moved file until the next check occurs, in the worst case this will happen recreate_check_interval seconds after the file has been moved or deleted. If this is undesirable, setting recreate_check_interval to 0 will have the appender check the file with every call to log().


In recreate mode, if this option is set to a signal name (e.g. "USR1"), the appender will recreate a missing logfile when it receives the signal. It uses less resources than constant polling. The usual limitation with perl's signal handling apply. Check the FAQ for using this option with the log rotating utility newsyslog.


The popular log rotating utility newsyslog expects a pid file in order to send the application a signal when its logs have been rotated. This option expects a path to a file where the pid of the currently running application gets written to. Check the FAQ for using this option with the log rotating utility newsyslog.


The file appender typically creates its logfile in its constructor, i.e. at Log4perl init() time. This is desirable for most use cases, because it makes sure that file permission problems get detected right away, and not after days/weeks/months of operation when the appender suddenly needs to log something and fails because of a problem that was obvious at startup.

However, there are rare use cases where the file shouldn't be created at Log4perl init() time, e.g. if the appender can't be used by the current user although it is defined in the configuration file. If you set create_at_logtime to a true value, the file appender will try to create the file at log time. Note that this setting lets permission problems sit undetected until log time, which might be undesirable.


If you want Log4perl to print a header into every newly opened (or re-opened) logfile, set header_text to either a string or a subroutine returning a string. If the message doesn't have a newline, a newline at the end of the header will be provided.

Design and implementation of this module has been greatly inspired by Dave Rolsky's Log::Dispatch appender framework.


Copyright 2002-2013 by Mike Schilli <> and Kevin Goess <>.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


Please contribute patches to the project on Github:

Send bug reports or requests for enhancements to the authors via our

MAILING LIST (questions, bug reports, suggestions/patches):

Authors (please contact them via the list above, not directly): Mike Schilli <>, Kevin Goess <>

Contributors (in alphabetical order): Ateeq Altaf, Cory Bennett, Jens Berthold, Jeremy Bopp, Hutton Davidson, Chris R. Donnelly, Matisse Enzer, Hugh Esco, Anthony Foiani, James FitzGibbon, Carl Franks, Dennis Gregorovic, Andy Grundman, Paul Harrington, Alexander Hartmaier David Hull, Robert Jacobson, Jason Kohles, Jeff Macdonald, Markus Peter, Brett Rann, Peter Rabbitson, Erik Selberg, Aaron Straup Cope, Lars Thegler, David Viner, Mac Yang.

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