pal.c

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

static int
is_palindromic(const char *str, size_t n) {
	size_t i, j;

	if (n == 0)
		return 1;

	i = 0;
	j = n - 1;

	while (1) {
		while (i < j && !isalpha(str[i]))
			i++;

		while (i < j && !isalpha(str[j]))
			j--;

		if (i >= j)
			break;

		if (tolower(str[i]) != tolower(str[j]))
			return 0;

		i++;
		j--;
	}

	return 1;
}

int
main(int argc, char *argv[]) {
	int i;
	
	for (i = 1; i < argc; i++) {
		fputs(argv[i], stdout);
		if (is_palindromic(argv[i], strlen(argv[i])))
			puts(" is a palindrome.");
		else
			puts(" is not a palindrome.");
	}
}