Question

int main(int argc, char **argv) {
  char username[256];
  username = ?;
}

thanks~

Answer 1

You probably want to make username be a pointer, then you can just assign it:

int
main(int argc, const char *const *argv)
{
    const char *username;
    if (argc >= 2)
        username = argv[1];
    else
    {
        fprintf(stderr, "usage: %s username ...\n", argv[0]);
        return 2;
    }
    /* ... */
}

But if you really want to copy the contents of the array, you are looking for strncpy.