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From: feit@cs.odu.edu (Mark A. Feit)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Need help:Ctrl-C and Ctrl-Break
Message-ID: <FEIT.90Jul31141946@oswald.cs.odu.edu>
Date: 31 Jul 90 18:19:45 GMT
References: <1990Jul30.182430.7493@uokmax.uucp> <9627@tekigm2.MEN.TEK.COM>
	<1990Jul31.023745.1116@water.waterloo.edu> <5717@sbsvax.cs.uni-sb.de>
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Organization: Old Dominion University, Norfolk, VA
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In-reply-to: fs-info@sbsvax.cs.uni-sb.de's message of 31 Jul 90 10:57:18 GMT


In article <5717@sbsvax.cs.uni-sb.de> fs-info@sbsvax.cs.uni-sb.de (c/o Peter Gaal) writes:


   In article <1990Jul31.023745.1116@water.waterloo.edu>, nmouawad@water.waterloo.edu (Naji Mouawad) writes:
   > In article <9627@tekigm2.MEN.TEK.COM> dennisw@tekigm2.MEN.TEK.COM (Dennis G
   > Ward) writes:
   > 
   > >input.  What's the trick(s)?
   > >-- 
   > >Dennis Ward    dennisw@tekigm2.MEN.TEK.COM    C1-820    (206)253-5428
   > 
   > The best method I know of, is to trap interrupt 09h. Write a little routine
   > that does the following:
   > ["little" deleted]

   Hmm, with your suggestion, you have to do scancode processing yourself,
   but why shouldn't MSDOS do the work for you ?
   [Pseudocode Obliterated...  MS-DOS doesn't work for me.  Ptui!]

A quick solution in C that lets the runtime library do the dirty work:

-------------8<-----Trim Here------------------

	BOOL	break_flag = FALSE;

void ctrl_break( void )
{
	break_flag = TRUE;

	/* Do as little as possible in here...  DOS gets in a strange state
	   during interrupts and doesn't take kindly to I/O being done.*/

	signal( SIGINT, ctrl_break );
}

void ctrl_break_handler( void )	/* Or whatever you need... */
{
	signal( SIGINT, SIG_IGN );	/* Shut ^Break off completely...
					   Don't want recursive calls. */

	printf( "\n\nWHAM!  Ctrl-Break!\n\n" );
	break_flag = FALSE;

	/* Do your own thing in here */

	signal( SIGINT, ctrl_break );	/* Reset things */
}

main( int argc, char **argv )
{
	signal( SIGINT, ctrl_break );

	for ( ; ; ) {	/* forever */

		/* Your code here */

		if ( break_flag )
			handle_ctrl_break();

	}
}

-------------8<-----Trim Here------------------

A couple of suggestions:

1.  Implement the code to check on break_flag inside of something that
gets run very often.  For example, I have a routine that gets called
over and over while the system is waiting for a key.  This also means
that you can finish up critical operations and _then_ check for a
break.

2.  If you want to get rid of that nasty ^C on the screen, the only
way I can find is to freopen() stdout to NUL.  There's no other way as
far as I can see without horking the keyboard interrupt (messy) or
modifying your BIOS (out of the question).  If you're using some
screen I/O package, odds are it uses its own direct reads and writes
and stdout just sits idle anyway.


						- Mark

................................... ................................... 
: Mark A. Feit                     : feit@cs.odu.edu                  :
: Old Dominion University CS Dept. : feit@xanth.UUCP                  :
: Norfolk, Virginia, U.S.A., Earth : "So where's my lunch, anyway?"   :
................................... ................................... 
  Y
:)8 G-G-G-D-E-C

--

						- Mark

................................... ................................... 
: Mark A. Feit                     : feit@cs.odu.edu                  :
: Old Dominion University CS Dept. : feit@xanth.UUCP                  :
: Norfolk, Virginia, U.S.A., Earth : "So where's my lunch, anyway?"   :
................................... ................................... 
  Y
:)8 G-G-G-D-E-C