SEMOP(2) | System Calls Manual | SEMOP(2) |
semop
— semaphore
operations
#include
<sys/sem.h>
int
semop
(int
semid, struct sembuf
*sops, size_t
nsops);
semop
()
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_NOWAIT
IPC_NOWAIT
makes the call return immediately, returning a value of -1 and setting
errno to EAGAIN
.SEM_UNDO
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:
EINVAL
]EIDRM
]EACCES
]E2BIG
]<sys/sem.h>
.EFBIG
]ENOSPC
]SEM_UNDO
was requested, and there is not enough space left in the kernel to store
the undo information.EAGAIN
]IPC_NOWAIT
was set in
sem_flg.EFAULT
]November 1, 2015 | OpenBSD-6.1 |