Caesars Cipher in C - c

Question

In this caesars cipher code how do i make it so that it reads in spaces, special characters (!##$*...), and numbers and keeps them as they are and prints them? Also i put an fprintf(file2,"\n") at the end of the fgets while loop and it does start a new line but it always prints a weird character at the end of the previous line.
#include <stdio.h>
int main (int argc, char *argv[]) {
char caesar[256];
int shift;
FILE *file1=fopen(argv[1],"r");
FILE *file2=fopen(argv[2],"w");
sscanf(argv[3], "%d", &shift);
while(fgets(caesar,sizeof(caesar),file1)!=NULL){
int i = 0;
while (caesar[i] != '\0') {
if (((caesar[i] + shift) >= 65 && (caesar[i] + shift) <= 90)||((caesar[i] + shift) >= 97 && (caesar[i] + shift) <= 122)) {
caesar[i] += (shift);
}
else {
caesar[i] += (shift - 26);
}
i++;
}
fprintf(file2,"%s", caesar);
fprintf(file2,"\n");
}
return 0;
}

Answer 1

#include <stdio.h>
#include <ctype.h>
int main (int argc, char *argv[]) {
char caesar[256];
int shift;
FILE *file1=fopen(argv[1],"r");
FILE *file2=fopen(argv[2],"w");
sscanf(argv[3], "%d", &shift);
while(fgets(caesar,sizeof(caesar), file1)!=NULL){
char ch;
int i = 0;
for(i = 0; (ch=caesar[i]) != '\0'; ++i) {
if (isalpha(ch)) {//Only alphabet
char a, z;
if(isupper(ch)){
a = 'A'; z = 'Z';
} else {
a = 'a'; z = 'z';
}
caesar[i] += shift;//this depend on the sequence of character codes.
if(caesar[i] > z){
caesar[i] = a + caesar[i] - z - 1;
}
}
}
fprintf(file2, "%s", caesar);
}
return 0;
}