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IPC-using fork() in a loop

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Top Forums Programming IPC-using fork() in a loop
# 1  
Old 09-01-2010
IPC-using fork() in a loop
I need to write a program which creates some n number of processes first and also creates a fifo for each of them, then it connects to the server and..

I tried creating these processes with fork() in a for loop but it doesn't print out what i write inside the child..
Code:
   for(int count = 0; count < nIntClientCount; count++)
   {
      pid_t pid;

      if((pid = fork()) < 0){
          perror("fork failed\n");
        exit(1);
      }else if(pid == 0)
      {   
         if((pid = fork()) < 0)
         {
                  perror("inner fork failed\n");
                    exit(1);
         }
         else if(pid > 0)
         exit(0);
          //second child body

            printf("I am CHILD %d", count);
      }
     if(waitpid(pid, NULL, 0) != pid) 
    perror("wait pid didn't match\n");
   }


   

  sleep(2);
  printf("parent exited..\n");

  return 0;

//--------------------------
i also tried the code without using 2 forks, but it also didnt print anything, plz help me



Moderator's Comments:
Mod Comment Please use code tags, thank you
Last edited by Franklin52; 09-01-2010 at 08:31 AM..
# 2  
Old 09-01-2010
Try to add
Code:
fflush(stdout);

After each call of printf()
# 3  
Old 09-01-2010
fflush(stdout) does not even help
Quote:
Originally Posted by dawwin
Try to add
Code:
fflush(stdout);

After each call of printf()
I did but again i get the same result, printf does not print anything and i don't know what happens to the childs...

[root@localhost Randomized Dissemination]# ./a.out
downloader peers randomly selected
parent exited..
# 4  
Old 09-01-2010
After add
Code:
exit(0);

after
Code:
printf("I am CHILD %d\n", count);

It prints this on my computer
Code:
I am CHILD 0
I am CHILD 1
I am CHILD 2
parent exited..

What system you've got?
# 5  
Old 09-01-2010
I tried it both on CentOS 5.2 and Ubuntu

plz have a look at my code again

Code:
   for(int count = 0; count < nIntClientCount; count++)
   {
      pid_t pid;

      if((pid = fork()) < 0){
          perror("fork failed\n");
            exit(1);
      }else if(pid == 0)
      {
         if((pid = fork()) < 0)
         {
                          perror("inner fork failed\n");
                                exit(1);
         }
         else if(pid > 0)
                exit(0);
          //second child body

            printf("I am CHILD %d\n", count);
            fflush(stdout);
      }
     if(waitpid(pid, NULL, 0) != pid)
        perror("wait pid didn't match\n");
   }

  printf("parent exited..\n");

  return 0;
}

Last edited by pludi; 09-01-2010 at 12:42 PM..
# 6  
Old 09-01-2010
Moderators have had to edit you for code tags so many times you've got negative bits. The formatting on your code is also all ruined because you didn't use code tags. PLEASE USE CODE TAGS. IT'S NOT HARD.

You haven't posted the complete program, either, I'm having to write a large part of it myself to make it work.

Your program, with nIntClientCount=3, gives this output:
Code:
I am CHILD 0
wait pid didn't match
: No child processes
I am CHILD 1
I am CHILD 1
wait pid didn't match
: No child processes
wait pid didn't match
: No child processes
I am CHILD 2
I am CHILD 2
wait pid didn't match
: No child processes
wait pid didn't match
: No child processes
parent exited..
parent exited..
parent exited..
parent exited..
I am CHILD 2
wait pid didn't match
: No child processes
parent exited..
I am CHILD 2
parent exited..
wait pid didn't match
: No child processes
parent exited..
parent exited..

# 7  
Old 09-01-2010
i cannot go inside child process
I just want to create n number of childs and after each child would start executing some instruction, but when i execute the program i don't receive anything, I wonder how you get the result.
my linux system is
Code:
CentOS 5.2

do u know how i can solve the problem?
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