C program that simulates the (deprecated) HTML <marquee> tag

marquee.c

#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

bool rflag = false;
float speed = 0.05;
char *str;

size_t str_len;
char *buf;

int usage() {
  fprintf(stderr, "usage: marquee [-h] [-r] [-s speed] 'text'\n");
  return 1;
}

void make_payload(size_t cols) {
  buf = malloc(str_len + cols + 2);
  for (size_t i = 0; i < cols; i++) {
    buf[i] = ' ';
  }
  buf[cols] = '\0';
  strcat(buf, str);
  strcat(buf, " ");
}

void print_payload(size_t cols) {
  char *ptr = buf;
  while (*ptr) {
    printf("\r%.*s", (int)cols, ptr);
    ptr++;
    if ((unsigned long)(ptr - buf) > cols + str_len) {
      if (rflag)
        ptr = buf;
      else
        break;
    }
    usleep(speed * 1000000);
  }
}

void cleanup() {
  fputs("\x1b[?25h\x1b[F", stdout);
  free(buf);
  exit(0);
}

int main(int argc, char *argv[]) {
  if (argc < 2)
    return usage();

  // warn if stdout isn't a tty
  if (!isatty(STDOUT_FILENO))
    fprintf(stderr, "warning: stdout is not a tty\n");

  // call cleanup() on SIGINT or SIGQUIT
  signal(SIGINT, cleanup);
  signal(SIGQUIT, cleanup);

  // get size of the terminal window
  struct winsize win;
  ioctl(0, TIOCGWINSZ, &win);

  // disable buffering and hide cursor
  setbuf(stdout, NULL);
  fputs("\x1b[?25l", stdout);

  // getopt
  char ch;
  while ((ch = getopt(argc, argv, "rs:h")) != -1) {
    switch (ch) {
    case 'r':
      rflag = true;
      break;
    case 's':
      speed = atof(optarg);
      break;
    case '?':
    case 'h':
    default:
      return usage();
    }
  }
  if (argv[optind] == NULL)
    return usage();
  str = argv[optind];
  str_len = strlen(str);

  make_payload(win.ws_col);
  print_payload(win.ws_col);

  cleanup();
}