NAME

mq_setattr — set message queue attributes (REALTIME)

SYNOPSIS

[MSG] #include <mqueue.h>

int mq_setattr(mqd_t mqdes, const struct mq_attr *restrict mqstat,
       struct mq_attr *restrict omqstat);

DESCRIPTION

The mq_setattr() function shall set 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 shall be set to the specified values upon successful completion of mq_setattr():

mq_flags

The value of this member is the bitwise-logical OR of zero or more of O_NONBLOCK and any implementation-defined flags.

The values of the mq_maxmsg, mq_msgsize, and mq_curmsgs members of the mq_attr structure shall be ignored by mq_setattr().

If omqstat is non-NULL, the mq_setattr() function shall store, in the location referenced by omqstat, the previous message queue attributes and the current queue status. These values shall be the same as would be returned by a call to mq_getattr() at that point.

RETURN VALUE

Upon successful completion, the function shall return a value of zero and the attributes of the message queue shall have been changed as specified.

Otherwise, the message queue attributes shall be unchanged, and the function shall return a value of -1 and set errno to indicate the error.

ERRORS

The mq_setattr() function shall fail if:

[EBADF]

The mqdes argument is not a valid message queue descriptor.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

mq_open, mq_send, msgctl, msgget, msgrcv, msgsnd

XBD <mqueue.h>

CHANGE HISTORY

First released in Issue 5. Included for alignment with the POSIX Realtime Extension.

Issue 6

The mq_setattr() function is marked as part of the Message Passing option.

The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Message Passing option.

The mq_timedsend() function is added to the SEE ALSO section for alignment with IEEE Std 1003.1d-1999.

The restrict keyword is added to the mq_setattr() prototype for alignment with the ISO/IEC 9899:1999 standard.