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Thread(3)	       Perl Programmers	Reference Guide		     Thread(3)

       Thread -	Manipulate threads in Perl (for	old code only)

       The "Thread" module served as the frontend to the old-style thread
       model, called 5005threads, that was introduced in release 5.005.	 That
       model was deprecated, and has been removed in version 5.10.

       For old code and	interim	backwards compatibility, the "Thread" module
       has been	reworked to function as	a frontend for the new interpreter
       threads (ithreads) model.  However, some	previous functionality is not
       available.  Further, the	data sharing models between the	two thread
       models are completely different,	and anything to	do with	data sharing
       has to be thought differently.  With ithreads, you must explicitly
       "share()" variables between the threads.

       You are strongly	encouraged to migrate any existing threaded code to
       the new model (i.e., use	the "threads" and "threads::shared" modules)
       as soon as possible.

       In Perl 5.005, the thread model was that	all data is implicitly shared,
       and shared access to data has to	be explicitly synchronized.  This
       model is	called 5005threads.

       In Perl 5.6, a new model	was introduced in which	all is was thread
       local and shared	access to data has to be explicitly declared.  This
       model is	called ithreads, for "interpreter threads".

       In Perl 5.6, the	ithreads model was not available as a public API; only
       as an internal API that was available for extension writers, and	to
       implement fork()	emulation on Win32 platforms.

       In Perl 5.8, the	ithreads model became available	through	the "threads"
       module, and the 5005threads model was deprecated.

       In Perl 5.10, the 5005threads model was removed from the	Perl

	   use Thread qw(:DEFAULT async	yield);

	   my $t = Thread->new(\&start_sub, @start_args);

	   $result = $t->join;

	   if ($t->done) {

	   if($t->equal($another_thread)) {
	       # ...


	   my $tid = Thread->self->tid;


	   my @list = Thread->list;

       The "Thread" module provides multithreading support for Perl.

       $thread = Thread->new(\&start_sub)
       $thread = Thread->new(\&start_sub, LIST)
	       "new" starts a new thread of execution in the referenced
	       subroutine. The optional	list is	passed as parameters to	the
	       subroutine. Execution continues in both the subroutine and the
	       code after the "new" call.

	       "Thread->new" returns a thread object representing the newly
	       created thread.

       lock VARIABLE
	       "lock" places a lock on a variable until	the lock goes out of

	       If the variable is locked by another thread, the	"lock" call
	       will block until	it's available.	 "lock"	is recursive, so
	       multiple	calls to "lock"	are safe--the variable will remain
	       locked until the	outermost lock on the variable goes out	of

	       Locks on	variables only affect "lock" calls--they do not	affect
	       normal access to	a variable. (Locks on subs are different, and
	       covered in a bit.)  If you really, really want locks to block
	       access, then go ahead and tie them to something and manage this
	       yourself.  This is done on purpose.  While managing access to
	       variables is a good thing, Perl doesn't force you out of	its
	       living room...

	       If a container object, such as a	hash or	array, is locked, all
	       the elements of that container are not locked. For example, if
	       a thread	does a "lock @a", any other thread doing a
	       "lock($a[12])" won't block.

	       Finally,	"lock" will traverse up	references exactly one level.
	       "lock(\$a)" is equivalent to "lock($a)",	while "lock(\\$a)" is

       async BLOCK;
	       "async" creates a thread	to execute the block immediately
	       following it.  This block is treated as an anonymous sub, and
	       so must have a semi-colon after the closing brace. Like
	       "Thread->new", "async" returns a	thread object.

	       The "Thread->self" function returns a thread object that
	       represents the thread making the	"Thread->self" call.

	       Returns a list of all non-joined, non-detached Thread objects.

       cond_wait VARIABLE
	       The "cond_wait" function	takes a	locked variable	as a
	       parameter, unlocks the variable,	and blocks until another
	       thread does a "cond_signal" or "cond_broadcast" for that	same
	       locked variable.	The variable that "cond_wait" blocked on is
	       relocked	after the "cond_wait" is satisfied.  If	there are
	       multiple	threads	"cond_wait"ing on the same variable, all but
	       one will	reblock	waiting	to re-acquire the lock on the
	       variable.  (So if you're	only using "cond_wait" for
	       synchronization,	give up	the lock as soon as possible.)

       cond_signal VARIABLE
	       The "cond_signal" function takes	a locked variable as a
	       parameter and unblocks one thread that's	"cond_wait"ing on that
	       variable. If more than one thread is blocked in a "cond_wait"
	       on that variable, only one (and which one is indeterminate)
	       will be unblocked.

	       If there	are no threads blocked in a "cond_wait"	on the
	       variable, the signal is discarded.

       cond_broadcast VARIABLE
	       The "cond_broadcast" function works similarly to	"cond_signal".
	       "cond_broadcast", though, will unblock all the threads that are
	       blocked in a "cond_wait"	on the locked variable,	rather than
	       only one.

       yield   The "yield" function allows another thread to take control of
	       the CPU.	The exact results are implementation-dependent.

       join    "join" waits for	a thread to end	and returns any	values the
	       thread exited with.  "join" will	block until the	thread has
	       ended, though it	won't block if the thread has already

	       If the thread being "join"ed "die"d, the	error it died with
	       will be returned	at this	time. If you don't want	the thread
	       performing the "join" to	die as well, you should	either wrap
	       the "join" in an	"eval" or use the "eval" thread	method instead
	       of "join".

       detach  "detach"	tells a	thread that it is never	going to be joined
	       i.e.  that all traces of	its existence can be removed once it
	       stops running.  Errors in detached threads will not be visible
	       anywhere	- if you want to catch them, you should	use
	       $SIG{__DIE__} or	something like that.

       equal   "equal" tests whether two thread	objects	represent the same
	       thread and returns true if they do.

       tid     The "tid" method	returns	the tid	of a thread. The tid is	a
	       monotonically increasing	integer	assigned when a	thread is
	       created.	The main thread	of a program will have a tid of	zero,
	       while subsequent	threads	will have tids assigned	starting with

       done    The "done" method returns true if the thread you're checking
	       has finished, and false otherwise.

       The following were implemented with 5005threads,	but are	no longer
       available with ithreads.

	       With 5005threads, you could also	"lock" a sub such that any
	       calls to	that sub from another thread would block until the
	       lock was	released.

	       Also, subroutines could be declared with	the ":locked"
	       attribute which would serialize access to the subroutine, but
	       allowed different threads non-simultaneous access.

       eval    The "eval" method wrapped an "eval" around a "join", and	so
	       waited for a thread to exit, passing along any values the
	       thread might have returned and placing any errors into $@.

       flags   The "flags" method returned the flags for the thread - an
	       integer value corresponding to the internal flags for the

       threads,	threads::shared, Thread::Queue,	Thread::Semaphore

perl v5.32.0			  2020-06-14			     Thread(3)


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