SYS$WAITFR (OpenVMS) SYS$WAITFR (OpenVMS)
NAME
semop - perform semaphore operations
SYS$WAITFR - Wait for single event flag
EXPLAINATION
The Digital UNIX semop system call is similar to the OpenVMS SYS$WAITFR
system service in that they both cause a process to wait while attempt‐
ing a process synchronization operation. The semop function can be
called with the sem_op field set to a negative number (indicating a
decrement to the semaphore value). If the semaphore value would become
less than zero, the calling process blocks until the operation can be
done such that the resulting semaphore value remains nonnegative. When
using a binary semaphore (to emulate an event flag) the sem_op value
would typically be set to -1 to indicate that the calling process
wishes to wait until another process either uses semctl to explicitly
set the semaphore to 1 or semop with a positive 1 sem_op.
RELATED INFORMATION
Digital UNIX Functions:
semop(2), semget(2), semctl(2) delim off
SYS$WAITFR (OpenVMS)
