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Subroutine: WKEY

Purpose: Write keywords to a task parameter list

Category: USER-INTERFACE

File: srvreq.c

Author: J.P. Terlouw

Use: CALL WKEY( TEXT ) Input, character

TEXT A character string containing keywords and
values, optionally prefixed by a taskname

Description: This routine writes keyword-value pairs to the parameter
list of the calling task or, if the name of a different
active task is specified, to the parameter list of that task.

Writing to the own parameter list is the most common.
It can be used to pass parameter information back and forth
between members of a chain of tasks initiated via calls to
DEPUTY. It is also used in event-driven programs in
connection the GIPSY's graphical user interface (Ggi).

Writing to an other task's parameter list can be useful when
one task needs to influence an other task. For example a
processing task could cause a display task to display
the processed data. In this mode of operation, the calling
task will wait until the addressed task has read all keywords
written with this call or until the addressed task exits.

In case of error, no action is performed and WKEY just returns.

Examples: a) "bare" call:
CALL WKEY('POS=PC, SET=0,1 PRINT=YES')

b) Suppose TASK1 computes the value of a parameter PARM1
which is needed as input to TASK2 which is called via
DEPUTY. Then in TASK1 the programmer codes:

PROGRAM TASK1
CHARACTER*20 STRING
.
.
PARM1=...
WRITE(STRING,'(''KEY1='',F10.4)') PARM1
CALL WKEY(STRING)
CALL DEPUTY('TASK2',IER)
.
.
END

The task receiving the keyword could be coded as
follows:

PROGRAM TASK2
.
.
N = USERREAL(VALUE,1,0,'KEY1=','Value, please')
.
.
.
END

Note that TASK2 calls USRINP in a standard way and
that it is unaware of the fact that the keyword has
been prepared by its caller.

c) In a similar way it is also possible that a spawned
task prepares keywords for its caller:

PROGRAM TASK1
.
.
CALL DEPUTY('TASK2',IER)
N = USERINT(...,'KEY=',...)
.
.
.
END

PROGRAM TASK2
.
.
CALL WKEY('KEY=...')
.
.
END

d) Write to other task:
CALL WKEY('SLICEVIEW READSUB=YES')

Related docs: DEPUTY.DC2, SUBST.DC2

Updates: Sep 4, 1981: JPT, Original document.
Feb 15, 1990: JPT, Portable version, rewritten in ANSI C.
Jan 16, 2001: JPT, Implement writing to other tasks.