ui.c

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/**
 * Project 1 "UI" example
 */

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

void percentage_bar(float value, char buf[30])
{
    if (value < 0.0) value = 0.0;
    if (value > 1.0) value = 1.0;

    char bar[] = "--------------------";
    int hashes = (int) (value * strlen(bar));

    for (int i = 0; i < hashes; i++) {
        bar[i] = '#';
    }
    snprintf(buf, 30, "[%s] %.1f%%", bar, value * 100);
}

int main(void)
{
    unsigned int counter = 0;
    while (true)
    {
        // Option 1 to create our "UI": clear the screen each iteration, and
        // redraw the whole thing. We can clear the string with this xterm
        // control sequence:
        //printf("\033[2J");

        char bar_buf[30] = { 0 };
        percentage_bar(rand() / (float) RAND_MAX, bar_buf);

        puts("");
        printf("Hostname: %s\n", "???");
        printf("  Kernel: %s\n", "???");
        printf("    CPUs: %s\n", "???");
        printf("  Memory: %s\n", "???");
        puts("");

        // If we expect a number to be a certain size, we can add padding after
        // it to ensure any old values are overwritten (mainly if the number
        // gets smaller... won't happen in this example):
        printf(" Counter: %-*d\n", 10, counter++);

        // Add extra space after the bar to clean up the previously-printed
        // value (in case the new value is a smaller string than the previous)
        printf("     Bar: %s  \n", bar_buf);
        puts("");

        // Wait 1 second to redraw.
        sleep(1);

        // Option 2, which can look a bit nicer. Instead of clearing the whole
        // screen, simply move back up and overwrite the old values in place:
        printf("\033[%dA", 9); // move the cursor up 9 lines
    }

    return 0;
}