netbsd man page for sem_wait

SEM_WAIT(3)						   BSD Library Functions Manual 					       SEM_WAIT(3)

NAME
     sem_wait, sem_trywait -- decrement (lock) a semaphore

LIBRARY
     POSIX Real-time Library (librt, -lrt)

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 indi-
     cate 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_post(3)

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

BSD
								 January 22, 2003							       BSD