parallel.c

#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>

// TODO:
// - parse max number
// - parse commands
// execute commands

// int main(int argc, char **argv)
int main()
{
  // if (argc < 2)
  // {
  //   write(2, "Invalid parameters\n", 20);
  //   exit(1);
  // }

  const char *a[4];
  a[0] = "sleep 2 ; echo second";
  a[1] = "sleep 4 ; echo fourth | sed s:four:4:g";
  a[2] = "echo f1rst";
  a[3] = "sleep 1 ; echo third";

  int tasks = 4;
  int maxParallel = 2;

  int currentExecutingTasks = 0;
  int current = 0;
  int status = 0;

  int pid2[tasks];

  while (current < tasks)
  {
    if (currentExecutingTasks < maxParallel)
    {
      pid2[current] = fork();

      if (pid2[current] == 0)
      {
        system(a[current]);

        currentExecutingTasks--;
        exit(0);
      }
      else
      {
        currentExecutingTasks++;
        current++;
      }
    }
    else
    {
      wait(NULL);
      currentExecutingTasks--;
    }
  }

  while ((wait(&status)) > 0)
  {
  };

  return 0;
}