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MSGGET(2) FreeBSD System Calls Manual MSGGET(2) NAME msgget - get message queue SYNOPSIS #include <sys/msg.h> int msgget(key_t key, int msgflg); DESCRIPTION msgget() returns the message queue identifier associated with key. A message queue identifier is a unique integer greater than zero. A message queue is created if either key is equal to IPC_PRIVATE, or key does not have a message queue identifier associated with it, and the IPC_CREAT bit is set in msgflg. If a new message queue is created, the data structure associated with it (the msqid_ds structure, see msgctl(2)) is initialized as follows: o msg_perm.cuid and msg_perm.uid are set to the effective UID of the calling process. o msg_perm.gid and msg_perm.cgid are set to the effective GID of the calling process. o msg_perm.mode is set to the lower 9 bits of msgflg. o msg_cbytes, msg_qnum, msg_lspid, msg_lrpid, msg_rtime, and msg_stime are set to 0. o msg_qbytes is set to the system wide maximum value for the number of bytes in a queue (MSGMNB). o msg_ctime is set to the current time. RETURN VALUES Upon successful completion a positive message queue identifier is returned. Otherwise, -1 is returned and the global variable errno is set to indicate the error. ERRORS [EACCES] A message queue is already associated with key and the caller has no permission to access it. [EEXIST] Both IPC_CREAT and IPC_EXCL are set in msgflg, and a message queue is already associated with key. [ENOSPC] A new message queue could not be created because the system limit for the number of message queues has been reached. [ENOENT] IPC_CREAT was not set in msgflg and no message queue associated with key was found. SEE ALSO msgctl(2), msgrcv(2), msgsnd(2), ftok(3) STANDARDS The msgget() function conforms to the X/Open System Interfaces option of IEEE Std 1003.1-2008 ("POSIX.1"). HISTORY Message queues first appeared in AT&T System V Release 1 UNIX and have been available since NetBSD 1.0. FreeBSD 14.1-RELEASE-p8 July 18, 2019 FreeBSD 14.1-RELEASE-p8