sem_getvalue(3) - NetBSD Manual Pages

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SEM_GETVALUE(3)         NetBSD Library Functions Manual        SEM_GETVALUE(3)


NAME

     sem_getvalue -- get the value of a semaphore


LIBRARY

     POSIX Real-time Library (librt, -lrt)


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

     sem_getvalue() will fail if:

     [EINVAL]           sem points to an invalid semaphore.


SEE ALSO

     sem_post(3), sem_timedwait(3), sem_trywait(3), sem_wait(3)


STANDARDS

     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 word-
     ing of the specification.

NetBSD 9.4                     February 29, 2012                    NetBSD 9.4