Sets message queue attributes.
Standard C Library (libc.a)
#include <mqueue.h>
int mq_setattr (mqdes, mqstat, omqstat)
mqd_t mqdes;
const struct mq_attr *mqstat;
struct mq_attr *omqstat; The mq_setattr subroutine sets attributes associated with the open message queue description referenced by the message queue descriptor specified by mqdes.
The message queue attributes corresponding to the following members defined in the mq_attr structure are set to the specified values upon successful completion of the mq_setattr subroutine.
The value of the mq_flags member is either zero or O_NONBLOCK.
The values of the mq_maxmsg, mq_msgsize, and mq_curmsgs members of the mq_attr structure are ignored by the mq_setattr subroutine.
If the omqstat parameter is non-NULL, the mq_setattr subroutine stores, in the location referenced by omqstat, the previous message queue attributes and the current queue status. These values are the same as would be returned by a call to the mq_getattr subroutine at that point.
| Item | Description |
|---|---|
| mqdes | Specifies the message queue descriptor. |
| mqstat | Specifies the status of the message queue. |
| omqstat | Specifies the status of the previous message queue. |
Upon successful completion, the mq_setattr subroutine returns a zero and the attributes of the message queue are changed as specified.
Otherwise, the message queue attributes are unchanged, and the subroutine returns a -1 and sets errno to indicate the error.
| Item | Description |
|---|---|
| EBADF | The mqdes parameter is not a valid message queue descriptor. |
| EFAULT | Invalid user address. |
| EINVAL | The mqstat parameter value is not valid. |
| ENOMEM | Insufficient memory for the required operation. |
| ENOTSUP | This function is not supported with processes that have been checkpoint-restart'ed. |