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Annotation of coherent/a/usr/man/COHERENT/msg, revision 1.1.1.1

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                      3: msg                       Device Driver                       msg
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                      8: Message device driver
                      9: 
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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
                     30: 
                     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 );
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                     63: 
                     64: COHERENT Lexicon                                           Page 1
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                     68: 
                     69: msg                       Device Driver                       msg
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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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