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$FreeBSD$
.Dd March 3, 2008 .Dt SEM_TIMEDWAIT 3 .Os .Sh NAME .Nm sem_timedwait .Nd "lock a semaphore" .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS n semaphore.h .Ft int .Fn sem_timedwait "sem_t *sem" "const struct timespec *abs_timeout" .Sh DESCRIPTION The .Fn sem_timedwait function locks the semaphore referenced by .Fa sem , as in the .Xr sem_wait 3 function. However, if the semaphore cannot be locked without waiting for another process or thread to unlock the semaphore by performing a .Xr sem_post 3 function, this wait will be terminated when the specified timeout expires.
p The timeout will expire when the absolute time specified by .Fa abs_timeout passes, as measured by the clock on which timeouts are based (that is, when the value of that clock equals or exceeds .Fa abs_timeout ) , or if the absolute time specified by .Fa abs_timeout has already been passed at the time of the call.
p Note that the timeout is based on the .Dv CLOCK_REALTIME clock.
p The validity of the .Fa abs_timeout is not checked if the semaphore can be locked immediately. .Sh RETURN VALUES The .Fn sem_timedwait function returns zero if the calling process successfully performed the semaphore lock operation on the semaphore designated by .Fa sem . If the call was unsuccessful, the state of the semaphore is unchanged, and the function returns a value of -1 and sets the global variable .Va errno to indicate the error. .Sh ERRORS The .Fn sem_timedwait function will fail if: l -tag -width Er t Bq Er EINVAL The .Fa sem argument does not refer to a valid semaphore, or the process or thread would have blocked, and the .Fa abs_timeout parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million. t Bq Er ETIMEDOUT The semaphore could not be locked before the specified timeout expired. t Bq Er EINTR A signal interrupted this function. .El .Sh SEE ALSO .Xr sem_post 3 , .Xr sem_trywait 3 , .Xr sem_wait 3 , .Xr sem 4 .Sh STANDARDS The .Fn sem_timedwait function conforms to .St -p1003.1-2004 . .Sh HISTORY The function first appeared in .Fx 5.0 .