fusl/src/string/strlcat.c

#define _BSD_SOURCE
#include <string.h>

size_t strlcat(char* d, const char* s, size_t n) {
  size_t l = strnlen(d, n);
  if (l == n)
    return l + strlen(s);
  return l + strlcpy(d + l, s, n - l);
}