AT&T UNIX™PC Unix System V Users Manual - tenox

MSGGET (2) MSGGET (2)
NAME msgget - get message queue
SYNOPSIS
#include
#include
#include
int msgget {key, msgflg)
key_t key;
int msgflg;
DESCRIPTION
Msgget returns the message queue identifier associated with key.
A message queue identifier and associated message queue and data
structure (see intro(2)) are created for key if one of the following
are true:
Key is equal to IPC_PRIVATE.
Key does not already have a message queue identifier
associated with it, and (msgftg & IPC_CREAT) is "true".
Upon creation, the data structure associated with the new message
queue identifier is initialized as follows:
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 low-order 9 bits of msg_perm.mode are set equal to
the low-order 9 bits of msgftg .
Msg_qnum, msg_lspid, msg_lrpid, msg_stime, and
msg_rtime are set equal to 0.
Msg_ctime is set equal to the current time.
Msg_qbytes is set equal to the system limit.
Msgget will fail if one or more of the following are true:
A message queue identifier exists for key but operation
permission (see intro(2)) as specified by the low-order 9
bits of msgftg would not be granted. [EACCESI
A message queue identifier does not exist for key and
(msgftg & IPC_CREAT) is "false". [ENOENTI
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.
[ENOSPCI
A message queue identifier exists for key but ( ( msgftg &
IPC_CREAT) & { msgftg & IPC_EXCL) ) is "true".
[EEXISTI
RETURN VALUE
Upon successful completion, a non-negative integer, namely a message
queue identifier, is returned. Otherwise, a value of - 1 is
returned and errno is set to indicate the error.
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