No newline at end of file when entering diff command on vi - c

Question

I'm so tired of debugging and changing my code but every time it gives me:
No newline at end of file
when I try:
diff main.c output.txt
My program encrypts/decrypts the input textfile and it gives a correct output when it converts but when I enter diff main.c output.txt then it would always point me to that error. What should I do to prevent that? Any help would be appreciated!
int encryptFile(FILE *input, FILE *output){
char c;
char p;
int r = 0;
char p1 = 0;
char c1 = 0;
int index = 0;
char line[100];
// while((p = fgetc(input)) != EOF){
while(fgets(line, sizeof(line), input) != NULL){
for(index = 0; line[index] != 0; index++){
p = line[index];
r = rand() % 97;
if(p == 't'){
p1 = 0;
}
else if(p == '\n'){
p1 = 1;
}
else{
p1 = p - 30;
}
c1 = p1 ^ r;
if(c1 == 0){
c = 't';
}
else if(c1 == 1){
c = '\n';
}
else{
c = c1 + 30;
}
//Write
fputc(c, output);
}
}
return 1;
}

Answer 1

Try adding a new line at the end of your output file:
int encryptFile(FILE *input, FILE *output)
{
char c = 0;
char p;
int r = 0;
char p1 = 0;
char c1 = 0;
int index = 0;
char line[100];
while (fgets(line, sizeof(line), input) != NULL) {
for (index = 0; line[index] != 0; index++) {
p = line[index];
r = rand() % 97;
//change all displayable characters [0...96]
if (p == 't') {
p1 = 0;
} else if (p == '\n') {
p1 = 1;
} else {
p1 = p - 30;
}
c1 = p1 ^ r;//bitwise xor
if (c1 == 0) {
c = 't';
} else if (c1 == 1) {
c = '\n';
} else {
c = c1 + 30;
}
//Write
fputc(c, output);
}
}
if (c != '\n') {
fputc('\n', output);
}
return 1;
}
Or use:
diff --ignore-all-space file1 file2