Example of a VT100 progress bar in C

progress_bar.c

//
//  progress_bar.c
//
//  Created by Leptos on 2/17/19.
//  Copyright © 2018 Leptos. All rights reserved.
//

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

int main(int argc, const char *argv[]) {
    const char *argOne = argv[1];
    if (argOne) {
        long const parsedInput = atol(argOne);
        if (parsedInput < 0) {
            puts("length cannot be negative");
            return 1;
        }
        
        size_t const len = parsedInput;
        char buff[len + 4];
        buff[0] = '[';
        memset(buff + 1, ' ', len);
        buff[len + 1] = ']';
        buff[len + 2] = '\r';
        buff[len + 3] = '\0';
        
        ptrdiff_t const buffOffset = 1;
        for (ptrdiff_t i = buffOffset; i < (len + buffOffset); i++) {
            buff[i] = '-';
            fputs(buff, stdout);
            fflush(stdout);
            usleep(100000);
        }
    } else {
        printf("Usage: %s <length>\n"
               "    Print a line of dashes (-) over time for a given length\n"
               "    This program is an example of a moving \"progress bar\" in a terminal\n", argv[0]);
    }
}