Pthread Join Linux Manual Page

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NAME|SYNOPSIS|DESCRIPTION|RETURNVALUE|ERRORS|ATTRIBUTES|

CONFORMINGTO|NOTES|EXAMPLE|SEEALSO|COLOPHON

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PTHREAD_JOIN(3)LinuxProgrammer'sManualPTHREAD_JOIN(3)

NAMEtop

pthread_join‐joinwithaterminatedthread

SYNOPSIStop

#include<pthread.h>

intpthread_join(pthread_tthread,void**retval);

Compileandlinkwith‐pthread.

DESCRIPTIONtop

Thepthread_join()functionwaitsforthethreadspecifiedbythread

toterminate.Ifthatthreadhasalreadyterminated,then

pthread_join()returnsimmediately.Thethreadspecifiedbythread

mustbejoinable.

IfretvalisnotNULL,thenpthread_join()copiestheexitstatusof

thetargetthread(i.e.,thevaluethatthetargetthreadsuppliedto

pthread_exit(3))intothelocationpointedtoby*retval.Ifthe

targetthreadwascanceled,thenPTHREAD_CANCELEDisplacedin

*retval.

Ifmultiplethreadssimultaneouslytrytojoinwiththesamethread,

theresultsareundefined.Ifthethreadcallingpthread_join()is

canceled,thenthetargetthreadwillremainjoinable(i.e.,itwill

notbedetached).

RETURNVALUEtop

Onsuccess,pthread_join()returns0;onerror,itreturnsanerror

number.

ERRORStop

EDEADLK

Adeadlockwasdetected(e.g.,twothreadstriedtojoinwith

9/15/2016 pthread_join(3)Linuxmanualpage

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eachother);orthreadspecifiesthecallingthread.

EINVALthreadisnotajoinablethread.

EINVALAnotherthreadisalreadywaitingtojoinwiththisthread.

ESRCHNothreadwiththeIDthreadcouldbefound.

ATTRIBUTEStop

Foranexplanationofthetermsusedinthissection,see

attributes(7).

┌───────────────┬───────────────┬─────────┐

│Interface│Attribute│Value│

├───────────────┼───────────────┼─────────┤

│pthread_join()│Threadsafety│MT‐Safe│

└───────────────┴───────────────┴─────────┘

CONFORMINGTOtop

POSIX.1‐2001,POSIX.1‐2008.

NOTEStop

Afterasuccessfulcalltopthread_join(),thecallerisguaranteed

thatthetargetthreadhasterminated.

Joiningwithathreadthathaspreviouslybeenjoinedresultsin

undefinedbehavior.

Failuretojoinwithathreadthatisjoinable(i.e.,onethatisnot

detached),producesa"zombiethread".Avoiddoingthis,sinceeach

zombiethreadconsumessomesystemresources,andwhenenoughzombie

threadshaveaccumulated,itwillnolongerbepossibletocreatenew

threads(orprocesses).

Thereisnopthreadsanalogofwaitpid(‐1,&status,0),thatis,

"joinwithanyterminatedthread".Ifyoubelieveyouneedthis

functionality,youprobablyneedtorethinkyourapplicationdesign.

Allofthethreadsinaprocessarepeers:anythreadcanjoinwith

anyotherthreadintheprocess.

EXAMPLEtop

Seepthread_create(3).

9/15/2016 pthread_join(3)Linuxmanualpage

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SEEALSOtop

pthread_cancel(3),pthread_create(3),pthread_detach(3),

pthread_exit(3),pthread_tryjoin_np(3),pthreads(7)

COLOPHONtop

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