c/dreammachine/strobe.c

   1 /* strobe.c (<~Harvie 2oo9)
   2  * Dream Machine implementation for GNU/Linux
   3  * usage ./strobe [frequency]
   4  */
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <signal.h>
  10
  11 void signal_handler(int signo) {
  12         if(signo == SIGTERM || signo == SIGINT || signo == SIGQUIT) {
  13                 fputs("\033[0m" "\033[2J" "\033[0;0H", stdout); fflush(stdout); //restore default terminal settings
  14                 exit(0);
  15         }
  16 }
  17
  18 int main(int argc, char *argv[]) {
  19         //Settings
  20         char bg_black[]         = "\033[40m\033[1;37m"; //set black background
  21         char bg_white[]         = "\033[47m\033[1;30m"; //set white background
  22         char cls[]                              = "\033[2J" "\033[0;0H"; //clear screen and return to begining of it
  23         char format_str[]       = "%s%s" //"\033[40m\033[1;37m"
  24                 "Warning: this software can cause seizures. Use it on your own risk only! Don't forget to close your eyes! Running at %g Hz (Press ^C to exit)";
  25         double frequency = 10; //Hz
  26
  27         //Compute intervals
  28         int cache_size = 0;
  29         if(argc > 1) {
  30                 frequency = strtod(argv[1], NULL); //get frequency from argv[1] (if present)
  31                 cache_size += sizeof(argv[1]);
  32         }
  33         useconds_t half_interval = (1000000/frequency)/2; //uSeconds
  34
  35         //Pre-cache output strings
  36         cache_size += sizeof(bg_black) + sizeof(cls) + sizeof(format_str) + 5;
  37         char state_a[cache_size];
  38         char state_b[cache_size];
  39
  40         sprintf(state_a, format_str, bg_black, cls, frequency);
  41         sprintf(state_b, format_str, bg_white, cls, frequency);
  42
  43         //Register signals
  44         signal(SIGINT, signal_handler); signal(SIGTERM, signal_handler); signal(SIGQUIT, signal_handler);
  45
  46         //Main loop
  47         while(1) {
  48                 fputs(state_a, stdout);
  49                         fflush(stdout);
  50                         usleep(half_interval);
  51                         if(argc > 2) getchar(); //interactive strobe
  52                 fputs(state_b, stdout);
  53                         fflush(stdout);
  54                         usleep(half_interval);
  55         }
  56 }