sem_wait man page on OpenBSD

sem_wait man page on OpenBSD

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SEM_WAIT(3)		  OpenBSD Programmer's Manual		   SEM_WAIT(3)

NAME
     sem_wait, sem_trywait - decrement (lock) a semaphore

SYNOPSIS
     #include <semaphore.h>

     int
     sem_wait(sem_t *sem);

     int
     sem_trywait(sem_t *sem);

DESCRIPTION
     The sem_wait() function decrements (locks) the semaphore pointed to by
     sem, but blocks if the value of sem is zero, until the value is non-zero
     and the value can be decremented.

     The sem_trywait() function decrements (locks) the semaphore pointed to by
     sem only if the value is non-zero.	 Otherwise, the semaphore is not
     decremented and an error is returned.

RETURN VALUES
     The sem_wait() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     sem_wait() and sem_trywait() will fail if:

     [EINVAL]	   sem points to an invalid semaphore.

     Additionally, sem_trywait() will fail if:

     [EAGAIN]	   The semaphore value was zero, and thus could not be
		   decremented.

SEE ALSO
     sem_destroy(3), sem_getvalue(3), sem_init(3), sem_open(3), sem_post(3)

STANDARDS
     sem_wait() and sem_trywait() conform to ISO/IEC 9945-1:1996 (``POSIX'').

OpenBSD 4.9			 May 31, 2007			   OpenBSD 4.9

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