sem_getvalue(3C)

NAME
     sem_getvalue - get the value of a posix named or unnamed semaphore

SYNOPSIS
     #include <semaphore.h>
     int sem_getvalue(sem_t *sem, int *value);

DESCRIPTION
     sem_getvalue obtains the current value of the semaphore located at
     address sem, and stores it at address value. The returned value should be
     viewed as a snapshot only, useful for debugging.

     If the number stored at value is positive, then the semaphore is
     available.  If the number stored at value is zero, then the semaphore is
     not available.  If the number stored at value is negative, then the
     semaphore is not available and the absolute value of the number
     represents the number of processes currently blocked on the semaphore.

     The address sem may reside anywhere in the calling processes address
     space, but the process must have read and write access to sem.

     sem_getvalue will fail if the following is true:

     [EINVAL]    The semaphore located at address sem is not a valid posix
                 named or unnamed semaphore.

SEE ALSO
     sem_init(3C), sem_destroy(3C), sem_getvalue(3C), sem_post(3C),
     sem_wait(3C), sem_trywait(3C), sem_open(3C), sem_close(3C),
     sem_unlink(3C),

DIAGNOSTICS
     Upon successful completion, a value of 0 is returned to the calling
     process. Otherwise, a value of -1 is returned and errno is set to
     indicate the error.