sem_getvalue man page on FreeBSD

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SEM_GETVALUE(3)		 BSD Library Functions Manual	       SEM_GETVALUE(3)

     sem_getvalue — get the value of a semaphore

     Standard C Library (libc, -lc)

     #include <semaphore.h>

     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.

     The sem_getvalue() function will fail if:

     [EINVAL]		The sem argument points to an invalid semaphore.

     sem_post(3), sem_trywait(3), sem_wait(3), sem(4)

     The sem_getvalue() function 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 word‐
     ing of the specification.

BSD			       February 15, 2000			   BSD

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