Forked writevt from console-tools

writevt.c

/*
 * Mostly ripped off of console-tools' writevt.c
 */

#include <stdio.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

char *progname;

static int usage() {
	printf("Usage: %s ttydev text\n", progname);
	return 2;
}

int main(int argc, char **argv) {
	int fd, argi;
	char *term = NULL;
	char *text = NULL;
	size_t len = 0;

	progname = argv[0];

	argi = 1;

	if (argi < argc)
		term = argv[argi++];
	else {
		fprintf(stderr, "%s: no tty specified\n", progname);
		return usage();
	}

	if (argi < argc)
		text = argv[argi++];
	else {
		fprintf(stderr, "%s: no text specified\n", progname);
		return usage();
	}

	len = strlen(text);
	if (len == 1 && text[0] == '-') {
		text = alloca(1024);
		len = read(0, text, 1024);
	}

	if (argi != argc) {
		fprintf(stderr, "%s: too many arguments\n", progname);
		return usage();
	}

	fd = open(term, O_RDONLY);
	if (fd < 0) {
		perror(term);
		fprintf(stderr, "%s: could not open tty\n", progname);
		return 1;
	}

	while (len) {
		if (ioctl(fd, TIOCSTI, text)) {
			perror("ioctl");
			return 1;
		}
		text++;
		len--;
	}

	return ioctl(fd, TIOCFLUSH, NULL);
}

Copied from here: https://github.com/grawity/code/blob/master/thirdparty/writevt.c

Original writevt can be found in console-tools here: https://sourceforge.net/projects/lct/files/

This version adds - as an input filename, which causes (per POSIX convention) the text to come from stdin.