Standard function to replace character or substring in a char array? [duplicate]

Answer 1

There are not such functions in the standard libraries.

You can easily roll your own using strchr for replacing one single char, or strstr to replace a substring (the latter will be slightly more complex).

int replacechar(char *str, char orig, char rep) {
    char *ix = str;
    int n = 0;
    while((ix = strchr(ix, orig)) != NULL) {
        *ix++ = rep;
        n++;
    }
    return n;
}

This one returns the number of chars replaced and is even immune to replacing a char by itself

Answer 2

There is no direct function to do that. You have to write something like this, using strchr:

char* replace_char(char* str, char find, char replace){
    char *current_pos = strchr(str,find);
    while (current_pos){
        *current_pos = replace;
        current_pos = strchr(current_pos,find);
    }
    return str;
}

For whole strings, I refer to this answered question