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$FreeBSD$
.Dd April 4, 1996 .Dt PTHREAD_ONCE 3 .Os .Sh NAME .Nm pthread_once .Nd dynamic package initialization .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS n pthread.h
p pthread_once_t .Fa once_control = PTHREAD_ONCE_INIT; .Ft int .Fn pthread_once "pthread_once_t *once_control" "void (*init_routine)(void)" .Sh DESCRIPTION The first call to .Fn pthread_once by any thread in a process, with a given .Fa once_control , will call the .Fn init_routine with no arguments. Subsequent calls to .Fn pthread_once with the same .Fa once_control will not call the .Fn init_routine . On return from .Fn pthread_once , it is guaranteed that .Fn init_routine has completed. The .Fa once_control parameter is used to determine whether the associated initialization routine has been called.
p The function .Fn pthread_once is not a cancellation point. However, if .Fn init_routine is a cancellation point and is cancelled, the effect on .Fa once_control is as if .Fn pthread_once was never called.
p The constant .Fa PTHREAD_ONCE_INIT is defined by header n pthread.h .
p The behavior of .Fn pthread_once is undefined if .Fa once_control has automatic storage duration or is not initialized by .Fa PTHREAD_ONCE_INIT . .Sh RETURN VALUES If successful, the .Fn pthread_once function will return zero. Otherwise an error number will be returned to indicate the error. .Sh ERRORS None. .Sh STANDARDS The .Fn pthread_once function conforms to .St -p1003.1-96 .