sem_getvalue
NAME
sem_getvalue - get the value of a semaphore
SYNOPSIS
#include <semaphore.h> I int sem_getvalue(sem_t * sem , int * sval );
DESCRIPTION
R sem_getvalue ()
places the current value of the semaphore pointed to
sem
into the integer pointed to by
R sval .
If one or more processes or threads are blocked
waiting to lock the semaphore with
sem_wait(3),
POSIX.1-2001 permits two possibilities for the value returned in
R 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.
RETURN VALUE
R sem_getvalue ()
returns 0 on success;
on error, -1 is returned and
errno
is set to indicate the error.
ERRORS
EINVAL
sem
is not a valid semaphore.
CONFORMING TO
POSIX.1-2001.
NOTES
The value of the semaphore may already have changed by the time
R sem_getvalue ()
returns.
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