#include <string.h>

int replace_char_line(char *buf, int key, int *replacements_left) {
    int replaced = 0;
    for (size_t i = 0; buf[i] != '\0'; i++) {
        if ((unsigned char)buf[i] == (unsigned char)key &&
            *replacements_left > 0 &&
            buf[i] != '\n') {
            buf[i] = ' ';
            replaced++;
            (*replacements_left)--;
            }
    }
    return replaced;
}