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From: bruceb@amiga.UUCP (Bruce Barrett)
Newsgroups: net.micro.amiga
Subject: Re BREAK (and Ctrl-C using Lattice) /long/
Message-ID: <677@amiga.amiga.UUCP>
Date: Wed, 12-Feb-86 12:47:24 EST
Article-I.D.: amiga.677
Posted: Wed Feb 12 12:47:24 1986
Date-Received: Fri, 14-Feb-86 03:04:23 EST
Reply-To: bruceb@amiga.UUCP (Bruce Barrett)
Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030
Lines: 59

Ok, this is how a (Lattice) C program detects Control-C, or Control-D
keypresses, ... or ... BREAK task#, C ; BREAK task#, D ; BREAK task#, ALL
This is taken from the C manual errata shipped with V1.1 developers kits.
I presume it is (c) copyright 1985, 1986 Commodore-Amiga, Inc.

page 6-7: Following the paragraph that begins "The program exit....", add:

	  Programs can also be terminated by task interruption, if desired.
	  If the external int location Enable_Abort contains a nonzero 
	  value, a check for the characters Ctrl-C and Ctrl-D is made
	  whenever a call to one of the level-1 I/O functions is processed.

page 6-7 at the and of section 6.2.4 add:

	Detection of Ctrl-C and Ctrl-D is provided in the I/O library. If 
	the external integer location Enable_Abort is set to non-zero, a 
	check for these conditions is performed every time a level-1 I/O 
	call is made. If either of these keys were pressed, the 
	appropriate character is echoed to stdout, all level-1 files are 
	closed, and the program terminates. Programs that do not use 
	level-1 I/O or that wish to check more frequently may call the 
	function Chk_Abort(), which will return zero if neither of the 
	keys were pressed, or the signal value if either key was pressed. 
	Note that if Enable_Abort is non-zero a successful call to 
	Chk_Abort (either key had been pressed) will result in program 
	termination as described above.

	If either of these keys has been typed, the appropriate character 
	is  echoed to the console window,  all level-1 files are  closed, 
	and the program is terminated.   Programs that do not use level-1 
	I/O  or  that need to check more frequently for interruption  may 
	call the function Chk_Abort(),  which will return zero if neither 
	of the interrupt characters were typed, or the appropriate signal 
	value  (which  will  be  non-zero;  see  AmigaDOS  documentation) 
	otherwise.   Note  that  control does not return  to  the  caller 
	unless  Enable_Abort is zero;  if it is non-zero,  the program is 
	simply terminated as described above.   By default,  Enable_Abort 
	is  zero;  it  must  be forced to a non-zero value  in  order  to 
	activate  the interrupt checking.   

	To check for ^C/^D every time a level-1 I/O call is made.  Exit
	if found:
		Enable_Abort = 1;

	To check for ^C/^D (for example within a loop) and if found, have 
	C handle exiting for you:
		Enable_Abort = 1;
		Chk_Abort();
	
	To check for ^C/^D (for example within a loop) and if found, NOT 
	have C exit for you:
		Enable_Abort = 0;
		If (0 != Chk_Abort()) {
		    do_my_cleanup();
		    exit(1);
		    }


------- Bruce Barrett ---------