Appender::File

Section: User Contributed Perl Documentation (3)
Updated: 2021-02-08
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NAME

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

SYNOPSIS

    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");

DESCRIPTION

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 explicitly.

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.

OPTIONS

filename

Name of the log file.

mode

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

"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

"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 synchronisation measures like semaphores (see: Synchronized appender).

umask

Specifies the "umask" to use when creating the file, determining the file's permission settings. If set to 0022 (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.

owner

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.

group

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.

utf8

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,
    );

binmode

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).

recreate

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.

recreate_check_interval

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()".

recreate_check_signal

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".

recreate_pid_write

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".

create_at_logtime

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.

header_text

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.

mkpath

If this this option is set to true, the directory path will be created if it does not exist yet.

mkpath_umask

Specifies the "umask" to use when creating the directory, determining the directory's permission settings. If set to 0022 (default), new directory will be created with "rwxr-xr-x" permissions. If set to 0000, new directory will be created with "rwxrwxrwx" permissions.

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

LICENSE

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

AUTHOR

Please contribute patches to the project on Github:

    http://github.com/mschilli/log4perl

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

MAILING LIST (questions, bug reports, suggestions/patches): log4perl-devel@lists.sourceforge.net

Authors (please contact them via the list above, not directly): Mike Schilli <m@perlmeister.com>, Kevin Goess <cpan@goess.org>

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.