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sem_getvalue(3rt) [sunos man page]

sem_getvalue(3RT)					    Realtime Library Functions						 sem_getvalue(3RT)

NAME
sem_getvalue - get the value of a semaphore SYNOPSIS
cc [ flag... ] file... -lrt [ library... ] #include <semaphore.h> int sem_getvalue(sem_t *restrict sem, int *restrict sval); DESCRIPTION
The sem_getvalue() function updates the location referenced by the sval argument to have the value of the semaphore referenced by sem with- out affecting the state of the semaphore. The updated value represents an actual semaphore value that occurred at some unspecified time during the call, but it need not be the actual value of the semaphore when it is returned to the calling process. If sem is locked, then the value returned by sem_getvalue() is either zero or a negative number whose absolute value represents the number of processes waiting for the semaphore at some unspecified time during the call. The value set in sval may be 0 or positive. If sval is 0, there may be other processes (or LWPs or threads) waiting for the semaphore; if sval is positive, no process is waiting. RETURN VALUES
Upon successful completion, sem_getvalue() returns 0. Otherwise, it returns -1 and sets errno to indicate the error. ERRORS
The sem_getvalue() function will fail if: EINVAL The sem argument does not refer to a valid semaphore. ENOSYS The sem_getvalue() function is not supported by the system. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
semctl(2), semget(2), semop(2), sem_post(3RT), sem_wait(3RT), attributes(5), standards(5) SunOS 5.10 1 Nov 2003 sem_getvalue(3RT)

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sem_post(3RT)						    Realtime Library Functions						     sem_post(3RT)

NAME
sem_post - increment the count of a semaphore SYNOPSIS
cc [ flag... ] file... -lrt [ library... ] #include <semaphore.h> int sem_post(sem_t *sem); DESCRIPTION
The sem_post() function unlocks the semaphore referenced by sem by performing a semaphore unlock operation on that semaphore. If the semaphore value resulting from this operation is positive, then no threads were blocked waiting for the semaphore to become unlocked; the semaphore value is simply incremented. If the value of the semaphore resulting from this operation is 0, then one of the threads blocked waiting for the semaphore will be allowed to return successfully from its call to sem_wait(3RT). If the symbol _POSIX_PRIORITY_SCHEDULING is defined, the thread to be unblocked will be chosen in a manner appropriate to the scheduling policies and parameters in effect for the blocked threads. In the case of the schedulers SCHED_FIFO and SCHED_RR, the highest priority waiting thread will be unblocked, and if there is more than one highest priority thread blocked waiting for the semaphore, then the highest priority thread that has been waiting the longest will be unblocked. If the symbol _POSIX_PRIORITY_SCHEDULING is not defined, the choice of a thread to unblock is unspecified. RETURN VALUES
If successful, sem_post() returns 0; otherwise it returns -1 and sets errno to indicate the error. ERRORS
The sem_post() function will fail if: EINVAL The sem argument does not refer to a valid semaphore. ENOSYS The sem_post() function is not supported by the system. EOVERFLOW The semaphore value exceeds SEM_VALUE_MAX. USAGE
The sem_post() function is reentrant with respect to signals and may be invoked from a signal-catching function. The semaphore functional- ity described on this manual page is for the POSIX (see standards(5)) threads implementation. For the documentation of the Solaris threads interface, see semaphore(3C)). EXAMPLES
See sem_wait(3RT). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
sched_setscheduler(3RT), sem_wait(3RT), semaphore(3C), attributes(5), standards(5) SunOS 5.10 12 Feb 2003 sem_post(3RT)
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