NAME

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

SYNOPSIS

use Log::Log4perl::DateFormat;

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

# Simple time, resolution in seconds
my $time = time();
print $format->format($time), "\n";
    # => "17:02:39,000"

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

DESCRIPTION

Log::Log4perl::DateFormat is a low-level helper class for the advanced date formatting functions in Log::Log4perl::Layout::PatternLayout.

Unless you're writing your own Layout class like Log::Log4perl::Layout::PatternLayout, there's probably not much use for you to read this.

Log::Log4perl::DateFormat is a formatter which allows dates to be formatted according to the log4j spec on

http://jakarta.apache.org/log4j/docs/api/org/apache/log4j/PatternLayout.html

which allows the following placeholders to be recognized and processed:

Symbol Meaning              Presentation    Example
------ -------              ------------    -------
G      era designator       (Text)          AD
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)       '

For example, if you want to format the current Unix time in "MM/dd HH:mm" format, all you have to do is this:

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"

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.

SEE ALSO

AUTHOR

Mike Schilli, <log4perl@perlmeister.com>