DateFormat(3)

NAME
Log::Log4perl::DateFormat - Log4perl advanced date formatter helper class

SYNOPSIS
      # Either in a log4j.conf file ...
    log4perl.appender.Logfile.layout = \
        Log::Log4perl::Layout::PatternLayout
    log4perl.appender.Logfile.layout.ConversionPattern = %d{MM/dd HH:mm} %m

      # ... or via the PatternLayout class ...
    use Log::Log4perl::Layout::PatternLayout;
    my $layout = Log::Log4perl::Layout::PatternLayout->new(
        "%d{HH:mm:ss,SSS} %m");

      # ... or even directly with this helper class:
    use Log::Log4perl::DateFormat;
    my $format = Log::Log4perl::DateFormat->new("HH:mm:ss,SSS");
    my $time = time();
    print $format->format($time), "\n";
        # => "17:02:39,000"

DESCRIPTION
"Log::Log4perl::DateFormat" is a helper class for the advanced date formatting functions in "Log::Log4perl::Layout::PatternLayout", and adheres (mostly) to the log4j SimpleDateFormat spec available on

    http://download.oracle.com/javase/1.4.2/docs/api/java/text/SimpleDateFormat.html

It supports the following placeholders:

    Symbol Meaning              Presentation    Example
    ------ -------              ------------    -------
    G      era designator       (Text)          AD
    e      epoch seconds        (Number)        1315011604
    y      year                 (Number)        1996
    M      month in year        (Text & Number) July & 07
    d      day in month         (Number)        10
    h      hour in am/pm (1~12) (Number)        12
    H      hour in day (0~23)   (Number)        0
    m      minute in hour       (Number)        30
    s      second in minute     (Number)        55
    S      millisecond          (Number)        978
    E      day in week          (Text)          Tuesday
    D      day in year          (Number)        189
    F      day of week in month (Number)        2 (2nd Wed in July)
    w      week in year         (Number)        27
    W      week in month        (Number)        2
    a      am/pm marker         (Text)          PM
    k      hour in day (1~24)   (Number)        24
    K      hour in am/pm (0~11) (Number)        0
    z      time zone            (Text)          Pacific Standard Time
    Z      RFC 822 time zone    (Text)          -0800
    '      escape for text      (Delimiter)
    ''     single quote         (Literal)       '

    Presentation explanation:

    (Text): 4 or more pattern letters--use full form, < 4--use short or
            abbreviated form if one exists.

    (Number): the minimum number of digits. Shorter numbers are
              zero-padded to this amount. Year is handled
              specially; that is, if the count of 'y' is 2, the
              Year will be truncated to 2 digits.

    (Text & Number): 3 or over, use text, otherwise use number.

For example, if you want to format the current Unix time in "MM/dd HH:mm" format, all you have to do is specify it in the %d{...} section of the PatternLayout in a Log4perl configuration file:

    # log4j.conf
    # ...
    log4perl.appender.Logfile.layout = \
        Log::Log4perl::Layout::PatternLayout
    log4perl.appender.Logfile.layout.ConversionPattern = %d{MM/dd HH:mm} %m

Same goes for Perl code defining a PatternLayout for Log4perl:

    use Log::Log4perl::Layout::PatternLayout;
    my $layout = Log::Log4perl::Layout::PatternLayout->new(
        "%d{MM/dd HH:mm} %m");

Or, on a lower level, you can use the class directly:

    use Log::Log4perl::DateFormat;
    my $format = Log::Log4perl::DateFormat->new("MM/dd HH:mm");
    my $time = time();
    print $format->format($time), "\n";

While the new() method is expensive, because it parses the format strings and sets up all kinds of structures behind the scenes, followup calls to format() are fast, because "DateFormat" will just call localtime() and sprintf() once to return the formatted date/time string.

So, typically, you would initialize the formatter once and then reuse it over and over again to display all kinds of time values.

Also, for your convenience, the following predefined formats are available, just as outlined in the log4j spec:

    Format   Equivalent                     Example
    ABSOLUTE "HH:mm:ss,SSS"                 "15:49:37,459"
    DATE     "dd MMM yyyy HH:mm:ss,SSS"     "06 Nov 1994 15:49:37,459"
    ISO8601  "yyyy-MM-dd HH:mm:ss,SSS"      "1999-11-27 15:49:37,459"
    APACHE   "[EEE MMM dd HH:mm:ss yyyy]"   "[Wed Mar 16 15:49:37 2005]"

So, instead of passing

    Log::Log4perl::DateFormat->new("HH:mm:ss,SSS");

you could just as well say

    Log::Log4perl::DateFormat->new("ABSOLUTE");

and get the same result later on.

  Known Shortcomings
The following placeholders are currently not recognized, unless someone (and that could be you :) implements them:

    F day of week in month
    w week in year
    W week in month
    k hour in day
    K hour in am/pm
    z timezone (but we got 'Z' for the numeric time zone value)

Also, "Log::Log4perl::DateFormat" just knows about English week and month names, internationalization support has to be added.

Millisecond Times
More granular timestamps down to the millisecond are also supported, just provide the millsecond count as a second argument:

    # Advanced time, resultion in milliseconds
    use Time::HiRes;
    my ($secs, $msecs) = Time::HiRes::gettimeofday();
    print $format->format($secs, $msecs), "\n";
        # => "17:02:39,959"

LICENSE
Copyright 2002-2016 by Mike Schilli <m@perlmeister.com> and Kevin Goess <cpan@goess.org>.

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.