MirBSD manpage: sem_getvalue(3)

SEM_GETVALUE(3)            BSD Programmer's Manual             SEM_GETVALUE(3)


     sem_getvalue - get the value of a semaphore


     #include <semaphore.h>

     sem_getvalue(sem_t *sem, int *sval);


     The sem_getvalue() function sets the variable pointed to by sval to the
     current value of the semaphore pointed to by sem, as of the time that the
     call to sem_getvalue() is actually run.


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


     sem_getvalue() will fail if:

     [EINVAL]      sem points to an invalid semaphore.


     sem_destroy(3), sem_init(3), sem_open(3), sem_post(3), sem_wait(3)


     sem_getvalue() conforms to ISO/IEC 9945-1:1996 ("POSIX.1").

     The value of the semaphore is never negative, even if there are threads
     blocked on the semaphore. POSIX is somewhat ambiguous in its wording with
     regard to what the value of the semaphore should be if there are blocked
     waiting threads, but this behavior is conformant, given the wording of
     the specification.

MirBSD #10-current            February 15, 2000                              1

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