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Annotation of coherent/a/usr/man/COHERENT/msg, revision 1.1

1.1     ! root        1: 
        !             2: 
        !             3: msg                       Device Driver                       msg
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        !             8: Message device driver
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        !            11: The file  /dev/msg is an interface to  the message device driver.
        !            12: It is  assigned major device 25  (minor device 0) and  can be ac-
        !            13: cessed as a character-special device.
        !            14: 
        !            15: All messaging operations  are performed through the COHERENT sys-
        !            16: tem call  ioctl.  Each of the  operations msgctl, msgget, msgsnd,
        !            17: and msgrcv  is performed with an integer  array as its parameter.
        !            18: The first  element of the array is reserved  for the return value
        !            19: (default,  -1).  Subsequent  elements  represent arguments.   The
        !            20: call to  ioctl passes  MSGCTL, MSGGET,  MSGSND, or MSGRCV  as the
        !            21: second argument,  and an array  of parameters as  the third argu-
        !            22: ment.  The first argument is an open file descriptor to /dev/msg.
        !            23: 
        !            24: Prior to accessing the devices, a entry must be created in direc-
        !            25: tory /dev, as follows:
        !            26: 
        !            27: 
        !            28: /etc/mknod /dev/msg c 25 0
        !            29: /bin/chmod 444 /dev/msg
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        !            31: 
        !            32: ***** Notes *****
        !            33: 
        !            34: The total space allocated for  message text (NNMMSSGG * NNMMSSCC) must be
        !            35: less than 64 kilobytes.
        !            36: 
        !            37: Allocation of too many message queues (NNMMSSQQIIDD) or messages (NNMMSSGG)
        !            38: can exhaust  kernel data space,  thus preventing the  system from
        !            39: running.  Recommended safe limits are NNMMSSQQIIDD=16 and NNMMSSGG=100.
        !            40: 
        !            41: Private message queues are not supported.  Message queues must be
        !            42: removed manually when no longer required.  Queue identifiers con-
        !            43: sist of  a scaled slot number plus a  slot usage sequence number.
        !            44: Using the system call msgctl with the option IPC_STAT will obtain
        !            45: information on the specified slot, even when it returns an error.
        !            46: 
        !            47: To remove  all message  queues, compile  and run the  following C
        !            48: code:
        !            49: 
        !            50: 
        !            51: msgget( 0, 0 );    /* must do first */
        !            52: 
        !            53: 
        !            54: 
        !            55: for ( qid = 0x100; qid < 0x4000; qid += 0x100 ) {
        !            56:         struct msqid_ds msb;
        !            57:         msb.msg_perm.seq = 0;
        !            58:         msgctl( qid, IPC_STAT, &msb );
        !            59: 
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        !            63: 
        !            64: COHERENT Lexicon                                           Page 1
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        !            68: 
        !            69: msg                       Device Driver                       msg
        !            70: 
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        !            73: 
        !            74:         if ( msb.msg_perm.seq > 0 )
        !            75:                 msgctl (msb.msg_perm.seq, IPC_RMID, 0 );
        !            76: }
        !            77: 
        !            78: 
        !            79: To load msg use the command drvld.
        !            80: 
        !            81: ***** Files *****
        !            82: 
        !            83: /usr/include/sys/ipc.h
        !            84: /usr/include/sys/msg.h
        !            85: /dev/msg
        !            86: 
        !            87: ***** See Also *****
        !            88: 
        !            89: device drivers, drvld, msgctl(), msgget(), msgop()
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        !           130: COHERENT Lexicon                                           Page 2
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