CODEWITHSUNDEEP
clinuxprocess
Bornfree
Bornfree

Reputation: 878

Bring process to foreground

I have a process (which reads and writes to terminal type) that has been exec'd by a background process. I can see it using ps. Trying to bring it to foreground, this is what I attempted:

int main()

{

    FILE* fd = popen("pidof my_program","r");

    // ...
    // Some code to get the pid of my_program as mpid
    //...

    printf("pid of my_program is %d",mpid);
    signal(SIGTTOU, SIG_IGN);
    setpgid(mpid,0); // Set program group id to pid of process
    tcsetpgrp(0,mpid); // Give it terminal stdin access
    tcsetpgrp(1,mpid); // Give it terminal stdout access
    return 0;
}

It isn't working though. Can someone help me on this? Thanks.

Upvotes: 2

Views: 7297

Answers (2)

Shash
Shash

Reputation: 4260

When you have a process that is in the background or suspended, you can move it to the foreground with the fg command. By default, the process most recently suspended or moved to the background moves to the foreground. You can also specify which pid it is using to make it foreground.

Upvotes: 0

vulkanino
vulkanino

Reputation: 9134

You could do it the "soft" way, by calling the shell command fg and pass it the pid (adviced).

If you want to code it, this is how fg/bg is coded into bash (don't don't don't):

static int
fg_bg (list, foreground)
     WORD_LIST *list;
     int foreground;
{
  sigset_t set, oset;
  int job, status, old_async_pid;
  JOB *j;

  BLOCK_CHILD (set, oset);
  job = get_job_spec (list);

  if (INVALID_JOB (job))
    {
      if (job != DUP_JOB)
    sh_badjob (list ? list->word->word : _("current"));

      goto failure;
    }

  j = get_job_by_jid (job);
  /* Or if j->pgrp == shell_pgrp. */
  if (IS_JOBCONTROL (job) == 0)
    {
      builtin_error (_("job %d started without job control"), job + 1);
      goto failure;
    }

  if (foreground == 0)
    {
      old_async_pid = last_asynchronous_pid;
      last_asynchronous_pid = j->pgrp;  /* As per Posix.2 5.4.2 */
    }

  status = start_job (job, foreground);

  if (status >= 0)
    {
    /* win: */
      UNBLOCK_CHILD (oset);
      return (foreground ? status : EXECUTION_SUCCESS);
    }
  else
    {
      if (foreground == 0)
    last_asynchronous_pid = old_async_pid;

    failure:
      UNBLOCK_CHILD (oset);
      return (EXECUTION_FAILURE);
    }
}

Upvotes: 2

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