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From: allbery@ncoast.UUCP
Newsgroups: comp.sources.misc
Subject: program to force commands on another terminal (BSD only)
Message-ID: <8705291811.AA23508@ubvax.ub.com>
Date: Fri, 29-May-87 14:11:32 EDT
Article-I.D.: ubvax.8705291811.AA23508
Posted: Fri May 29 14:11:32 1987
Date-Received: Thu, 4-Jun-87 01:49:21 EDT
Lines: 144
Approved: allbery@ncoast.UUCP

This program lets a super-user enter commands or data on a terminal other
than his own.  Handy for logging people off -- just
	force ttyB4 logout
instead of 'ps auxt' and 'kill -HUP'.  Also more fun :-).  It is known to
run on 4.3 BSD; it will definitely run on 4.2 BSD; it may run on V7 or SIII
or even S5 -- basically, if you have TIOCSTI, you can use this.
I found this program in our public sources directory; it has no authorship
in the comments, which means it probably belongs to ATT :-), but it's simple
and short enough that it looks like it was done locally -- just way, way
before my time.

It was called 'type.c', but because it matches the function of a program in
my old Alpha-Micro days called "force", I call it that here.  The usage
message thinks it's called "type", so you can call it that, too, if you want.
Actually I don't care what you call it.

----------------------------cut here for force.c---------------------------
#include <sgtty.h>
#include <sys/file.h>
#include <stdio.h>
#include <sys/param.h>
#include <strings.h>

/*
 * type - make the system think that a command was entered on
 * another user's terminal.
 *
 * type [-n] <terminal> <command>
 *
 *	<terminal> is the line that the command should be entered on.
 *		examples: "/dev/ttyj4" ; "ttyj4" ; "j4"
 *
 *	<command> is the command that should be entered on that terminal.
 *		examples: "logout" ; "jobs > /dev/console"
 *
 * a newline will be appended to <command> unless type is given a "-n"
 * option.
 *
 * type can only be used on the terminal you are on, unless you are the
 * superuser, in which case you can send commands to any terminal.
 */

static int fd;		/* file descriptor for terminal line */
extern int wakeup();	/* routine to wakeup if open of terminal line hangs */

main(argc, argv, environ)
int argc;
char *argv[], *environ[];
{
	int flag_n;		/* do not append newline to <command> */

	if ( argc <= 1 ) {
		usage();
	}

	if ( argv[1][0] == '-' ) {
		switch ( argv[1][1] ) {
			case 'n' :
				flag_n++;
				break;
			case '-' :
				break;
			default:
				usage();
				break;
		}
		argc--, argv++;
	}
		
	if ( argc < 3 ) {
		usage();
	}

	if ( index( argv[1], '/' ) == NULL ) {
		char terminal[MAXPATHLEN+1];

		/*
		 * since a full pathname was not given, assume the
		 * file is in the "/dev" directory, and if only 2
		 * characters were given, assume that means a "tty".
		 */
		strcpy( terminal, "/dev/" );
		if (strlen(argv[1]) == 2)
			strcat( terminal, "tty" );
		argv[1] = strcat( terminal, argv[1] );
	}

	/*
	 * O_NDELAY does not work (?), so set a timer to
	 * wake up if the open hangs.
	 */
	
	signal( SIGALRM, wakeup );
	alarm( 30 );

	if ( (fd = open(argv[1], O_WRONLY|O_NDELAY, 0)) < 0 ) {
		perror( "open" );
		exit( 2 );
	} else {
		char *cp = argv[2];

		alarm( 0 );

		while ( *cp != '\0' ) {
			send( *cp );
			cp++;
		}

		if ( ! flag_n ) send( '\n' );
	}
}

usage()
{
	fprintf( stderr, "usage: type [-n] <terminal> <command>\n" );
	exit( 1 );
}

send( c )
char c;
{
	register int status;

	status = ioctl( fd, TIOCSTI, &c );

	if ( status != 0 ) {
		perror( "ioctl" );
		exit( 3 );
	}

	return status;
}

wakeup()
{
	fprintf( stderr, "open hung\n" );
	exit( 4 );
}
-----------------------------------cut here--------------------------------
-- 
Brandon S. Allbery	{decvax,cbatt,cbosgd}!cwruecmp!ncoast!allbery
Tridelta Industries	{ames,mit-eddie,talcott}!necntc!ncoast!allbery
7350 Corporate Blvd.	necntc!ncoast!allbery@harvard.HARVARD.EDU
Mentor, OH 44060	+01 216 255 1080	(also eddie.MIT.EDU)