/* 
	Program rotx ("Rotate X") performs a Caeser Cipher on text read from standard input,
	and writes the ciphertext to standard output.  Program encrypts one character at a
	time.

	John Nordlie, 1995
*/

#include<stdio.h>
#include<stdlib.h>

int main(int argc, char *argv[]) {
	int character, rotation;

	/* check for proper number of arguments, exit if not */
	if (argc != 2) {
		printf("Usage: rotx <rotation value> < <input file>\n");
		printf("or: <command outputting to stdout> | rotx <rotation value>\n");
		exit(1);
	}

	/* first argument is offset */
	rotation = atoi(argv[1]);

	/* get the first character */
	character = fgetc(stdin);

	/* main loop */
	while (!feof(stdin)) {

		/* if character in A - Z, rotate it */
		if ((character < 91)&&(character > 64)) {
			character = character + rotation;
			if (character > 90) {
				character = character - 26;
			}
		} else {
			/* if character in a - z, rotate it */
			if ((character < 123) && (character > 96)) {
				character = character + rotation;
				if (character > 122) {
					character = character - 26;
				}
			}
		}

		/* send possibly modified character to output */
		printf("%c", character);

		/* get the next input character */
		character = fgetc(stdin);

	} /* end if */

} /* end main */