str_replace.c

/*
 * Search and replace a string with another string , in a string
 * */
char *str_replace(char *search , char *replace , char *subject)
{
    char  *p = NULL , *old = NULL , *new_subject = NULL ;
    int c = 0 , search_size;
     
    search_size = strlen(search);
     
    //Count how many occurences
    for(p = strstr(subject , search) ; p != NULL ; p = strstr(p + search_size , search))
    {
        c++;
    }
     
    //Final size
    c = ( strlen(replace) - search_size )*c + strlen(subject);
     
    //New subject with new size
    new_subject = malloc( c );
     
    //Set it to blank
    strcpy(new_subject , "");
     
    //The start position
    old = subject;
     
    for(p = strstr(subject , search) ; p != NULL ; p = strstr(p + search_size , search))
    {
        //move ahead and copy some text from original subject , from a certain position
        strncpy(new_subject + strlen(new_subject) , old , p - old);
         
        //move ahead and copy the replacement text
        strcpy(new_subject + strlen(new_subject) , replace);
         
        //The new start position after this search match
        old = p + search_size;
    }
     
    //Copy the part after the last search match
    strcpy(new_subject + strlen(new_subject) , old);
     
    return new_subject;
}