|SEMOP(2)||System Calls Manual||SEMOP(2)|
semop — semaphore
semid, struct sembuf
provides a number of atomic operations on a set of semaphores. The semaphore
set is specified by semid. sops
is an array of semaphore operations, nsops is the
number of operations in this array. The sembuf
structures in the array contain the following members:
u_short sem_num; /* semaphore # */ short sem_op; /* semaphore operation */ short sem_flg; /* operation flags */
Each operation (specified in sem_op) is applied to semaphore number sem_num in the set of semaphores specified by semid. The value of sem_op determines the action taken in the following way:
The behavior of each operation is influenced by the flags set in sem_flg in the following way:
IPC_NOWAITmakes the call return immediately, returning a value of -1 and setting errno to
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
semop() will fail if:
SEM_UNDOwas requested, and there is not enough space left in the kernel to store the undo information.
IPC_NOWAITwas set in sem_flg.
|November 1, 2015||OpenBSD-6.9|