Async Module Script

hopper.c

#include <sys/ioctl.h>
#include <stdio.h>
#include <sys/poll.h>
#include <stdlib.h>
#include <string.h>

struct str_sized {
  size_t size;
  char* str;
};

int main(int argc, char** argv) {
  if (argc == 1) {
    puts("Usage: hopper program1 program2 ...");
    return 1;
  }

  // Shift out the name of the program
  argc--;
  argv++;
  // Create an array of file deescriptors to be monitored
  struct pollfd* plist = malloc(argc*sizeof(struct pollfd));
  FILE** flist = malloc(argc*sizeof(FILE*));
  struct str_sized* buffer = malloc(argc*sizeof(struct str_sized));
  int ret;
  int needupdate = 0;
  for (int i=0; i<argc; i++) {
    // Start the script
    flist[i] = popen(argv[i], "r");

    plist[i].fd = fileno(flist[i]);
    // Only monitor input events
    plist[i].events = POLLIN;

    buffer[i].size = 1;
    buffer[i].str = malloc(1);
  }

  for (;;) {
    // Wait for events
    ret = poll(plist, argc, -1);
    if (ret == -1) {
      perror("poll");
      return 1;
    }
    // Check which file descriptors have been updated
    for (int i=0; i<argc; i++) {
      // Remove closed file descriptors
      if (plist[i].revents & POLLHUP) {
        pclose(flist[i]);
        plist[i].fd = -1;
        plist[i].events = 0;
      }
      // Update if new data comes in
      else if (plist[i].revents & POLLIN) {
        getline(&buffer[i].str, &buffer[i].size, flist[i]);
        buffer[i].str[strlen(buffer[i].str)-1] = '\0';
        needupdate = 1;
      }
    }
    // Only output text when text has been updated
    if (needupdate) {
      for (int i=0; i<argc; i++)
        printf("%s", buffer[i].str);
      printf("\n");
      fflush(stdout);
      needupdate = 0;
    }
  }
}

usage.md

Installing hopper is very simple. First you must compile it using the following command: gcc hopper.c -o hopper And then move it to usr/bin/ so it can be executed.