setenv from c

[Chris Torek]

TIOCSTI works, but is unweildy and not very general.  In addition,
you must be careful not to overflow the TTY input queue.  Here is
a program I wrote long ago for saving and restoring C shell history
in, well, an `unusual fasion' which works around the latter problem.

#include <stdio.h>
#include <sgtty.h>
#include <ctype.h>

main(argc, argv)
	int argc;
	register char **argv;
{
	register char *hp, *cp;
	register FILE *in;
	register total = 0;
	static char histbuf[BUFSIZ], cmd[BUFSIZ + 5] = "!#:p ";
	struct sgttyb tty, otty;

	if (argc != 2) {
		fprintf(stderr, "Usage: %s file\n", argv[0]);
		exit(1);
	}
	if ((in = fopen(argv[1], "r")) == NULL) {
		fprintf(stderr, "%s: cannot open %s\n", argv[0], argv[1]);
		exit(1);
	}
	if (ioctl(0, TIOCGETP, &tty) < 0) {
		fprintf(stderr, "%s: not connected to a tty\n", argv[0]);
		exit(1);
	}
	switch (fork()) {
	case -1:
		fprintf(stderr, "%s: fork failed\n", argv[0]);
		exit(1);
	case 0:
		break;
	default:
		exit(0);
	}
	otty = tty;
	tty.sg_flags &= ~ECHO;
	(void) ioctl(0, TIOCSETN, &tty);
	while (fgets(histbuf, sizeof histbuf, in)) {
		if (cmd[5]) {
			for (cp = cmd; *cp; cp++)
				(void) ioctl(0, TIOCSTI, cp);
			if ((total += cp - cmd) >= 100) {/* fudge factor */
				sleep(1);
				total = 0;
			}
		}
		cp = cmd + 5;
		hp = histbuf;
		if (hp[6] == '\t' && isdigit(hp[5]))
			hp += 7;
		while (*cp++ = *hp++);
	}
	/*
	 * Note: drop last command as it was the one that dumped the history
	 * list.
	 */
	(void) ioctl(0, TIOCSETN, &otty);
	exit(0);
}
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris at umcp-cs		ARPA:	chris at mimsy.umd.edu