SEM_TIMEDWAIT(3)					   BSD Library Functions Manual 					  SEM_TIMEDWAIT(3)

NAME

     sem_timedwait -- lock a semaphore

LIBRARY

     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

     #include <semaphore.h>

     int
     sem_timedwait(sem_t *sem, const struct timespec *abs_timeout);

DESCRIPTION

     The sem_timedwait() function locks the semaphore referenced by sem, as in the 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 sem_post(3) function, this wait will be termi-
     nated when the specified timeout expires.

     The timeout will expire when the absolute time specified by abs_timeout passes, as measured by the clock on which timeouts are based (that
     is, when the value of that clock equals or exceeds abs_timeout), or if the absolute time specified by abs_timeout has already been passed at
     the time of the call.

     Note that the timeout is based on the CLOCK_REALTIME clock.

     The validity of the abs_timeout is not checked if the semaphore can be locked immediately.

RETURN VALUES

     The sem_timedwait() function returns zero if the calling process successfully performed the semaphore lock operation on the semaphore desig-
     nated by 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 errno to indicate the error.

ERRORS

     The sem_timedwait() function will fail if:

     [EINVAL]		The sem argument does not refer to a valid semaphore, or the process or thread would have blocked, and the abs_timeout
			parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.

     [ETIMEDOUT]	The semaphore could not be locked before the specified timeout expired.

     [EINTR]		A signal interrupted this function.

SEE ALSO

     sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS

     The sem_timedwait() function conforms to IEEE Std 1003.1-2004 (``POSIX.1'').

HISTORY

     The function first appeared in FreeBSD 5.0.

BSD
								   March 3, 2008							       BSD