replace ',' by 'c' in C - c

Question

Hello there I'm beginner and learning bases of C. I'm trying to replace all ',' that users could write by some '.' for my programm can run and read it. For now when I launch it doesn't took the number after the comma.
If I write in the console whit a dot it's okay
#include <stdio.h>
#include <stdlib.h>
#include "functiun.h"
#include <string.h>
int lire(char *chaine, int longueur)
{
char *positionEntree = NULL;
// On lit le texte saisi au clavier
if (fgets(chaine, longueur, stdin) != NULL) // Pas d'erreur de saisie ?
{
positionEntree = strchr(chaine, '\n');
if (positionEntree != NULL)
{
*positionEntree = '\0';
}
return 1;
}
else
{
return 0; // On renvoie 0 s'il y a eu une erreur
}
}
double lireDouble()
{
char nombreTexte[100] = {0}; // 100 cases devraient suffire
if (lire(nombreTexte, 100))
{
// Si lecture du texte ok, convertir le nombre en double et le retourner
return strtod (nombreTexte, NULL);
}
else
{
// Si problème de lecture, renvoyer 0
return 0;
}
}
double virgulePosition (char *chaine, int longueur)
{
char *virgulePosition = NULL;
if (fgets(chaine, longueur, stdin) != NULL)
{
virgulePosition = strchr(chaine, ',');
if (virgulePosition != NULL)
{
*virgulePosition = '.';
}
}
return strtod (chaine, NULL);
}

Answer 1

First off all try to do not mix code which does something with the I/O functions. For example the character replace is a great candidate to be a fuunction
char *strreplace(char *haystack, char needle, char replace)
{
char *saved = haystack;
if(haystack)
{
while(*haystack)
{
if(*haystack == needle) *haystack = replace;
haystack++;
}
}
return saved;
}