freebsd man page for sem_getvalue

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

NAME
     sem_getvalue -- get the value of a semaphore

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <semaphore.h>

     int
     sem_getvalue(sem_t * restrict sem, int * restrict sval);

DESCRIPTION
     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.

RETURN VALUES
     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.

ERRORS
     The sem_getvalue() function will fail if:

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

SEE ALSO
     sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS
     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
     wording of the specification.

BSD
								 February 15, 2000							       BSD