Tabs converter C

Question

I am trying to make a program that converts 4 spaces to tabs. But I have some bug I can't find.

Here is the code:

#include <stdio.h>
#define TABVALUE 4
#define ARRAYSIZE 3
int c, d, s;
int savedChars[ARRAYSIZE];

void emptyArray(int *a);

int main(void) {
    c = s = d = 0;
    while ((c = getchar()) != EOF) {
        if (c == ' ') {
            s = 0;
            s++;
            for (int j = 0; j < TABVALUE - 1; j++) {
                d = getchar();
                if (d != EOF) {
                    savedChars[j] = d;
                    savedChars[j + 1] = '\0';
                    if (d == ' ') {
                        s++;
                    } else {
                        break;
                    }
                }
            }
            if (s == TABVALUE) {
                emptyArray(savedChars);
                putchar('\t');
                s = 0;
            } else {
                putchar(c);
                for (int i = 0; i < 3; i++) {
                    if (savedChars[i] != '\0') {
                        putchar(savedChars[i]);
                    }
                }
            }
        } else {
            if (c != EOF) putchar(c);
        }
    }
    return 0;
}

void emptyArray(int *a) {
    for (int i = 0; i < ARRAYSIZE; i++) {//The bug is not in this function, i guess
        a[i] = '\0';
    }
}

Input:

2 spaces then character d 4 spaces then character d

Output:

2 spaces then character d 1 space then character d

But when I just add putchar(s) or anything like printf("a") before:

if (s == TABVALUE) {
                emptyArray(savedChars);
                putchar('\t');
                s = 0;
            }

than the output is this:

a 2 spaces d a tab d

Why is tab working when I print something? I am really confused...

Answer 1

Now you know that JetBrains doesn't always help, you should learn about tools like od -c or xxd -g 1 or some similar byte dump program so that you can see exactly what's in the output and avoid running into problems that turn out to be in your environment rather than the program you show on SO.

If I have some input text in input.txt. Do I do it like this?

./a.out<input.txt | od -cb

Yes. You might get output like this:

$ ./a.out <input.txt | od -cb
0000000            d  \t   d
          040 040 144 011 144
0000005
$

The leading 0000000 is the byte offset in the file. This is followed by two spaces (not very visible), a letter d, a tab and another d with no newline. The trailing 0000005 indicates that the total length of the file is 5 bytes. If you have a file with kilobytes or megabytes of data, the offset can be important. If you're trying to understand the binary structure of a file, the offsets can be important. For a 5-byte file, they're not very relevant.

The second line of triple digits is the octal representation of each character shown in the previous line (triggered by the -b option). Thus 040 is 32 decimal, or 0x20 hexadecimal, and is the code for a space; 144 corresponds to d, and 011 or 9 decimal corresponds to tab \t.

The output from xxd is loosely equivalent:

$ ./a.out < input.txt | xxd -g 1
00000000: 20 20 64 09 64                                     d.d
$

It shows the hex codes instead of the octal codes, and prints two spaces, a d, a dot (because the tab is not a graphic character) and another d.

Tools like these can be very useful for telling you about what data is in a file. There are other tools that can help, including sed l (equivalent to sed -e 'l') on all platforms, and cat -v on some platforms. Different tools have different emphases.

Answer 2

It has something to do with JetBrains.I was looking in output.txt(the file i saved output) in JetBrains.And it was space.But when i looked in normal notepad it was tab.Thats the only problem.I think there is no problem in code.