Thread: using popen

I'm using ubuntu 10.04

I'm writing a small program to read the input of a gamepad (ps3) that needs a driver (sixad). I used popen to create a process and run the driver in background. Also I want to know when the gamepad is connected, so I need to catch the sixad messages, I made popen("sixad -s (start) 2>&1, "r")) to read from both stdout and stderr. When I got the message that the gamepad is connected I was thinking in breaking the while loop, and to proceed with the rest of the program.
I tested the following code, but I don't understand the results (more below), why the loop isn't always running?.
I'm a complete newbie, I don't know if this is the correct way of doing what I want, so any suggestions will be very appreciated.

Code:

FILE *fp1;
  printf("popen\n"); 

  if ((fp1 = popen("sixad -s 2>&1","r")) == NULL)
  {
    fprintf(stderr, "Fail opening popen\n");
    exit(EXIT_FAILURE);
  }

  char linha[400];
  printf("\n1");
  while(fgets(linha,400,fp1)!=NULL)
  {
    printf("\n2");
    char *n=strstr(linha,"Connected PLAYSTATION(R)3 Controller");
    printf("\n3");
    printf("\n[%s]%s",n,linha);

    printf("\n4");
    if(n=='\0')
    {
      printf("\n5");
    }
    printf("\n6");
   }
  printf("\n7");

Terminal: when I don't press the PS button

1
2
3
[(null)]sixad[2114]: sixad started, press the PS button now

4
5

Terminal: when I press the PS button @5 and the gamepad is sucessfully connected

1
2
3
[(null)]sixad[2432]: sixad started, press the PS button now

4
5
6
2
3
[Connected PLAYSTATION(R)3 Controller (00:23:06:A4:E6:AA)
]sixad[2446]: Connected PLAYSTATION(R)3 Controller (00:23:06:A4:E6:AA)

4

And cross-posted across forums as well

@Salem

Thank you for the help.
Sorry for the cross posting. I didn't know the correct place to post.

Yes I want to break the loop because of waiting too long. What are real pipes btw? If you can get me some tutorials or indications about that I'll be very thankful.

@Salem

thank you once again.

I only need to use these 3 functions? and forget popen? how I launch the driver then? I have no experience with processes.. can you make me the basic code if isn't asking too much?