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26 .TH SEM_GETVALUE 3 2006-03-25 "Linux" "Linux Programmer's Manual"
28 sem_getvalue \- get the value of a semaphore
31 .B #include <semaphore.h>
33 .BI "int sem_getvalue(sem_t *" sem ", int *" sval );
36 Link with \fI\-lrt\fP or \fI\-pthread\fP.
39 places the current value of the semaphore pointed to
41 into the integer pointed to by
44 If one or more processes or threads are blocked
45 waiting to lock the semaphore with
47 POSIX.1-2001 permits two possibilities for the value returned in
50 or a negative number whose absolute value is the count
51 of the number of processes and threads currently blocked in
53 Linux adopts the former behavior.
57 on error, \-1 is returned and
59 is set to indicate the error.
64 is not a valid semaphore.
68 The value of the semaphore may already have changed by the time