winch.c

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

static void winch_handler(int);
static void print_tdim(void);

extern int
main()
{
	if (!isatty(STDIN_FILENO)) {
		perror("Looks like this isn't a terminal");
		return (1);
	}

	print_tdim();

	signal(SIGWINCH, winch_handler);

	/* wait for a signal */
	for (;;)
		pause();
}

static void
winch_handler(int n)
{
	(void)n; /* I don't care about n */

	print_tdim();

	signal(SIGWINCH, winch_handler); /* restore handler */
}

static void
print_tdim(void)
{
	struct winsize ws;

	/* Terminal IO Control Get WINdow SiZe */
	if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) != 0) {
		perror("Cannot get terminal size");
		exit (1);
	}

	printf("columns: %3d rows: %3d\n", ws.ws_col, ws.ws_row);
}