NAME

mq_setattr — set message queue attributes (REALTIME)

SYNOPSIS

#include <mqueue.h>

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

DESCRIPTION

The mq_setattr() function is used to 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 are 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-dependent flags.

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

If omqstat is non-NULL, the function mq_setattr() 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 mq_getattr() at that point.

RETURN VALUE

Upon successful completion, the function returns a value of zero and the attributes of the message queue will have been changed as specified. Otherwise, the message queue attributes are unchanged, and the function returns a value of -1 and sets errno to indicate the error.

ERRORS

The mq_setattr() function will fail if:

[EBADF]

The mqdes argument is not a valid message queue descriptor.

[ENOSYS]

The function mq_setattr() is not supported by this implementation.

EXAMPLES

None.

APPLICATION USAGE

None.

SEE ALSO

mq_open(3) , mq_send(3) , <mqueue.h> , msgctl(3) , msgget(3) , msgrcv(3) , msgsnd(3) .

DERIVATION

Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995)