sem_getvalue - get the value of a semaphore
int sem_getvalue(sem_t *sem, int *sval);
Link with -pthread
() places the current value of the semaphore pointed to
into the integer pointed to by sval
If one or more processes or threads are blocked waiting to lock the semaphore
, POSIX.1 permits two possibilities for the value
returned in sval
: either 0 is returned; or a negative number whose
absolute value is the count of the number of processes and threads currently
blocked in sem_wait(3)
. Linux adopts the former behavior.
() returns 0 on success; on error, -1 is returned and
is set to indicate the error.
- sem is not a valid semaphore.
For an explanation of the terms used in this section, see attributes(7)
The value of the semaphore may already have changed by the time
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