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msgget

SYNOPSIS

int msgget(key_t key, int msgflg);

PARAMETERS

key: [in] the message queue identifier to get.

msgflg: [in] some flags (see description).

DESCRIPTION

Gets a message queue identifier. If key is IPC_PRIVATE, a new queue is created, otherwise the result depends on msgflg. The possible values for msgflg are:

IPC_CREAT

creates a new queue for the key if it does not already exist.

IPC_EXCL

if there is already a existing queue associated with key, the call fails.

The 9 lower bits of msgflg specify the permission bits of the new queue. They have the same layout and meaning as those for files. However, the execute permissions are meaningless for queues.

When creating a queue the system sets the appropriate parameters in the msqid_ds structure associated with the new queue. When accessing an already existing queue, the system simply check if the queue can be accessed.

RETURN VALUE

On success, the call returns the new queue identificator. On error -1 is returned and errno is set to one of the following values:

• EACCESS: the task has no access permission to the queue.
• EEXIST: IPC_CREAT and IPC_EXCL were specified and the queue already exists.
• EIDRM: the message queue no longer exists in the system.
• ENOENT: the message queue never existed.
• ENOSPC: the maximum number of message queues for the system has been reached.
• ENOMEM

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