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From: reiner@jabberwock.shs.ohio-state.edu (Reiner Wilhelms)
Newsgroups: comp.unix.questions
Subject: Question on interprocess communication and signals
Keywords: interprocess communication, pipes, signals, notify procedure, SunView
Message-ID: <265@jabberwock.shs.ohio-state.edu>
Date: 29 Aug 90 19:41:00 GMT
Distribution: usa
Organization: The Ohio State University, Division of Speech and Hearing Science
Lines: 36

Question 1. 
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In signal.h are two signals defined:
#define SIGUSR1 30      /* user defined signal 1 */
#define SIGUSR2 31      /* user defined signal 2 */

How can they be generated?  (In the man pages I couldn't find a hint
to this.) Does this relate to the following problem, and to question 2?

The Problem:
------------
 I have one program, call it B, which reads a file of
vectors, displays them on the screen, and then enters an interactive
mode in which it is possible to perform geometric transformations of
the data - rotation, scaling etc.  As the program was designed for
SunView, it enters the SunView subroutine window_main_loop() after
building up a control panel and reading the data for display. It
remains in the window_main_loop until it exits. To make this program
read the next file for display, one could for example define a special
button which, when pressed, results in calling a subroutine to read
the file.  
Now I am writing another interactive program, call it A, which
generates the data for B.

Question 2: 
----------- 

How can one build a communication line between the two such that A
dials B, and says: "Hey, I have a new data set for you!" Essentially
program A "presses the read-new-data button" of program B.  What would
the notification routine look like, and what kind of signals could I
use to establish the cooperation of the two programs?

Any suggestions are highly appreciated. 

Reiner