GNU Readline: how to clear the input line?

Question

I use GNU Readline in the \"select\" fashion, by registering a callback function like so:

rl_callback_handler_install(\"\", on_readline_input);

Answer 1

After quite a lot of hacking I was able to get this mechanism. I hope other people will find it useful. It does not even use select(), but I hope you will get the point.

#include 
    #include 
    #include 
    #include 
    #include 

    const char const* prompt = "PROMPT> ";

    void printlog(int c) {
        char* saved_line;
        int saved_point;
        saved_point = rl_point;
        saved_line = rl_copy_text(0, rl_end);
        rl_set_prompt("");
        rl_replace_line("", 0);
        rl_redisplay();
        printf("Message: %d\n", c);
        rl_set_prompt(prompt);
        rl_replace_line(saved_line, 0);
        rl_point = saved_point;
        rl_redisplay();
        free(saved_line);
    }


    void handle_line(char* ch) {
        printf("%s\n", ch);
        add_history(ch);
    }

    int main() {
        int c = 1;

        printf("Start.\n");
        rl_callback_handler_install(prompt, handle_line);

        while (1) {
            if (((++c) % 5) == 0) {
                printlog(c);
            }

            usleep(10);
            rl_callback_read_char();
        }
        rl_callback_handler_remove();
    }