msgget() -- get message queue

SYNOPSIS

#include <sys/msg.h>

int msgget(key_t key, int msgflg);

The msgget() function returns the message queue identifier associated with key. A message queue identifier and an associated message queue and data structure are created if key is equal to IPC_PRIVATE, or key does not already have a message queue identifier associated with it and (msgflg & IPC_CREAT) is non-zero.

When created, the data structure associated with the new message queue identifier is initialized in the following way:

msg_perm.cuid, msg_perm.uid, msg_perm.cgid, and msg_perm.gid are set equal to the effective user ID and effective group ID, respectively, of the calling process.

The permission bits of msg_perm.mode are set to the permission bits of msgflg.

msg_qnum, msg_lspid, msg_lrpid, msg_stime, and msg_rtime are set to 0.

msg_ctime is set to the current time.

msg_qbytes is set to the system limit.

PARAMETERS

key: Specifies the message queue key for which to retrieve the msqid.
msgflg: Is a flag that indicates specific message queue conditions and options to implement.

RETURN VALUES

If successful, msgget() returns a message queue identifier. On failure, msgget() returns a value of -1 and sets errno to indicate the error:

EACCES: A message queue identifier exists for key, but operation permission as specified by permission bits of msgflg would not be granted.
EEXIST: A message queue identifier exists for key, but both (msgflg & IPC_CREAT) and (msgflg & IPC_EXCL) are both non-zero.
ENOENT: A message queue identifier does not exist for key and (msgflg & IPC_CREAT) is zero.
ENOSPC: A message queue identifier is to be created, but the system-imposed limit on the maximum number of allowed message queue identifiers system wide would be exceeded.

msgget()
get message queue

Function

SYNOPSIS

DESCRIPTION

PARAMETERS

RETURN VALUES

CONFORMANCE

MULTITHREAD SAFETY LEVEL

PORTING ISSUES

AVAILABILITY

SEE ALSO

msgget() get message queue

Function

msgget()
get message queue