Question

I’m attempting to remove a character from a string in C. The problem I am having with my code is that it removes the first instance of the character from the string but also wipes everything after that character in the string too. For example, removing ‘l’ from ‘hello’ prints ‘he’ rather than ‘heo’

int i;
char str1[30] = "Hello", *ptr1, c = 'l';
ptr1 = str1;
for (i=0; i<strlen(str1); i++)
{
    if (*ptr1 == c) *ptr1 = 0;
    printf("%c\n", *ptr1);
    ptr1++;
}

I need to use pointers for this and would like to keep it as simple as possible since I’m a beginner in C.
Thanks

Answer 1

You can do it like this:

void remove_all_chars(char* str, char c) {
    char *pr = str, *pw = str;
    while (*pr) {
        *pw = *pr++;
        pw += (*pw != c);
    }
    *pw = '\0';
}

int main() {
    char str[] = "llHello, world!ll";
    remove_all_chars(str, 'l');
    printf("'%s'\n", str);
    return 0;
}

The idea is to keep a separate read and write pointers (pr for reading and pw for writing), always advance the reading pointer, and advance the writing pointer only when it’s not pointing to a given character.