az priemam che razdeliteli sa ' ', '\t', '\n' ... za "\r\n" iska malko powehe pisane.

#include <stdio.h>

void main(int argc, char *argv[]) {
if(argc != 4) {
printf("Usage: crypt <file> <output> <key>\n");
return;
}
FILE *in = fopen(argv[1], "r");
if(in == NULL) {
printf("error openning file: %s\n", argv[1]);
return;
}
FILE *out = fopen(argv[2], "w");
if(out == NULL) {
printf("error openning file: %s\n", argv[2]);
return;
}
char key = argv[3][0];
char c;
char new;
int len = 0;
while( (c = fgetc(in)) != EOF ) {
if( c == ' ' || c == '\t' || c == '\n') {
len++;
new = c;
} else {
new = (c + key + len)%255;
}
fputc(new, out);
}
printf("len == %d", len);
fclose(in);
fclose(out);
}