10/16/84  watch

Syntax as a command:  watch {locations} {-control_args}


Function: manipulates the table of virtual memory locations under
scrutiny by the trace facility, which can monitor up to 1024 locations
for content changes.  The word at each location is checked whenever any
entrypoint in the trace table is called or returns.  When a change is
detected, execution is stopped and the old and new contents are
displayed.  (See trace.info for more information about the trace
facility.)


Arguments:
locations
   represent virtual memory locations in a form acceptable to the
   cv_ptr_ subroutine.  You must separate multiple locations by spaces
   (see "Notes on the syntax of locations").


Control arguments: tell what to do with the specified locations.  If
   you select neither -add nor -remove, -add is assumed.
-add
   adds the specified locations to the watch table.  When a location is
   added to the watch table, its content is saved there for later
   comparison; when a specified location is already in the watch table,
   its saved content is brought up to date.
-changed
   specifies all locations with content changes.
-remove, -rm
   removes the specified locations from the watch table.
-status, -st
   displays the specified locations and their contents from the watch
   table.


Notes: To prevent trace messages while watching, use the "-trace off"
argument to the trace command when adding entrypoints to the trace
table.

The order of entrypoints in the watch table is determined by their
segment numbers and word offsets.  The table is ordered first by
ascending segment number and then by ascending word offset.


All locations in the watch table are checked whenever any entrypoint in
the trace table is called or returns unless the entrypoint is off or
all tracing is disabled.  If any locations have changed, the trace
facility prints a stop message, displays the old and new contents, and
calls the -stop_proc.  When the -stop_proc returns, the new contents
are recorded in the watch table and execution resumes.  Unless you
change it, the -stop_proc is the command processor, so you can invoke a
debugger to get further information.  To get a trace of the changing
contents without stopping, use the command "trace -stop_proc nothing".


Notes on the syntax of locations: Acceptable representations include
the following:
   pathname|word_number
   pathname                   (same as pathname|0)
   pathname|entryname
   pathname$entryname         (pathname must contain > or <)
   reference_name$word_number
   reference_name$            (same as reference_name$0)
   reference_name$entryname
   segment_number|word_number
   segment_number              (same as segment_number|0)
   segment_number|entryname
   *                           (all locations in the watch table)


Pathnames can be relative or absolute.  All numbers are octal.  Bit
offsets are ignored.  If you use *, you can't specify any other
locations.


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Historical Background

This edition of the Multics software materials and documentation is provided and donated
to Massachusetts Institute of Technology by Group BULL including BULL HN Information Systems Inc. 
as a contribution to computer science knowledge.  
This donation is made also to give evidence of the common contributions of Massachusetts Institute of Technology,
Bell Laboratories, General Electric, Honeywell Information Systems Inc., Honeywell BULL Inc., Groupe BULL
and BULL HN Information Systems Inc. to the development of this operating system. 
Multics development was initiated by Massachusetts Institute of Technology Project MAC (1963-1970),
renamed the MIT Laboratory for Computer Science and Artificial Intelligence in the mid 1970s, under the leadership
of Professor Fernando Jose Corbato. Users consider that Multics provided the best software architecture 
for managing computer hardware properly and for executing programs. Many subsequent operating systems 
incorporated Multics principles.
Multics was distributed in 1975 to 2000 by Group Bull in Europe , and in the U.S. by Bull HN Information Systems Inc., 
as successor in interest by change in name only to Honeywell Bull Inc. and Honeywell Information Systems Inc. .

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Permission to use, copy, modify, and distribute these programs and their documentation for any purpose and without
fee is hereby granted,provided that the below copyright notice and historical background appear in all copies
and that both the copyright notice and historical background and this permission notice appear in supporting
documentation, and that the names of MIT, HIS, BULL or BULL HN not be used in advertising or publicity pertaining
to distribution of the programs without specific prior written permission.
    Copyright 1972 by Massachusetts Institute of Technology and Honeywell Information Systems Inc.
    Copyright 2006 by BULL HN Information Systems Inc.
    Copyright 2006 by Bull SAS
    All Rights Reserved