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MDC(3)		      User Contributed Perl Documentation		MDC(3)

       Log::Log4perl::MDC - Mapped Diagnostic Context

       Log::Log4perl allows loggers to maintain	global thread-specific data,
       called the Nested Diagnostic Context (NDC) and Mapped Diagnostic
       Context (MDC).

       The MDC is a simple thread-specific hash	table, in which	the
       application can stuff values under certain keys and retrieve them later
       via the "%X{key}" placeholder in

       Log::Log4perl::MDC->put($key, $value);
	   Store a value $value	under key $key in the map.

       my $value = Log::Log4perl::MDC->get($key);
	   Retrieve the	content	of the map under the specified key.  Typically
	   done	by %X{key} in "Log::Log4perl::Layout::PatternLayout".  If no
	   value exists	to the given key, "undef" is returned.

       my $text	= Log::Log4perl::MDC->remove();
	   Delete all entries from the map.

	   Returns a reference to the hash table.

       Please note that	all of the methods above are class methods, there's no
       instances of this class.	Since the thread model in perl 5.8.0 is	"no
       shared data unless explicitly requested"	the data structures used are
       just global (and	therefore thread-specific).

       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.

perl v5.24.1			  2017-02-21				MDC(3)


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