Search and replace programme with c doesn't work fine?

Question

hey everyone i have a problem to solve with c but the programme doesnt work fine this is the subject :

Write a program called search_and_replace that takes 3 arguments, the first arguments is a string in which to replace a letter (2nd argument) by another one (3rd argument). If the number of arguments is not 3, just display a newline. If the second argument is not contained in the first one (the string) then the program simply rewrites the string followed by a newline.

Examples:

$>./search_and_replace "Papache est un sabre" "a" "o"
Popoche est un sobre

and this the full code ;

#include <unistd.h>

int main(int argc, char **argv)
{
    int i;
    int j;
    int k;   
    int replace;

    i = 0;
    j = 0;
    if (argc == 4)
    {
        while(argv[1][i])
        {
            while(argv[2][j] != '\0' && argv[1][i] == argv[2][j])
            {
                while(argv[3][k])
                {
                    k = 0;
                    replace = argv[2][j];
                    argv[2][j] = argv[3][k];
                    argv[3][k] = replace;
                    k++;
                }
                argv[1][i] = argv[2][j];
                j++;
            }
            write(1, &argv[1][i], 1);
            i++;
        }
    }
}

i'm trying to change variables declaration inside the loops and also make all condition in juste 2 while

Answer 1

You have several unnecessary loops. The 2nd and 3rd arguments are just single characters, not strings that you need to loop over. You just replace any occurrences of argc[2][0] with argc[3][0].

You also don't need to swap characters between argv[2] and argv[3] when you find a match.

#include <unistd.h>
#include <string.h>

int main(int argc, char **argv)
{
    if (argc == 4 && strlen(argc[2]) > 0 && strlen(argc[3]) > 0)
    {
        char *string = argc[1];
        char old = argc[2][0];
        char new = argc[3][0];

        for (int i = 0; string[i]; i++) {
            if (string[i] == old) {
                string[i] = new;
            }
        }
        write(STDOUT_FILENO, string, strlen(string));
    }
    write(STDOUT_FILENO, "\n", 1); // write a newline after the replacement
}