msgget(2)                                               msgget(2)



NAME
     msgget - gets message queue

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ipc.h>
     #include <sys/msg.h>

     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 is true:

          key is equal to IPC_PRIVATE.

          key does not already have a message queue identifier
          associated with it, and (msgflg & IPC_CREAT) is
          ``true''.

     The key IPC_PRIVATE will create an identifier and associated
     data structure that is unique to the calling process and its
     children.

     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 msgflg.

          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.

STATUS MESSAGES AND VALUES
     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.



January 1992                                                    1

msgget(2)                                               msgget(2)



     The msgget command will fail if one or more of the following
     is true:

     EACCES
          A message queue identifier exists for key, but
          operation permission (see intro(2)) as specified by the
          low-order 9 bits of msgflg would not be granted.

     ENOENT
          A message queue identifier does not exist for key and
          (msgflg & IPC_CREAT) is ``false.''

     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.

     EEXIST
          A message queue identifier exists for key but ((msgflg
          & IPC_CREAT) && (msgflg & IPC_EXCL)) is ``true.''

SEE ALSO
     intro(2), msgctl(2), msgop(2)































2                                                    January 1992