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SEM_GETVALUE(3) BSD Library Functions Manual SEM_GETVALUE(3)
sem_getvalue -- get the value of a semaphore
POSIX Real-time Library (librt, -lrt)
sem_getvalue(sem_t * restrict sem, int * restrict 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_post(3), sem_trywait(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 sema-
phore. POSIX is somewhat ambiguous in its wording with regard to what the value of the sem-
aphore should be if there are blocked waiting threads, but this behavior is conformant,
given the wording of the specification.
BSD January 22, 2003 BSD
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