process sequence

[zooro]

hello ...I dont know if here is the right place for my question :
Write a C program linear.c that creates a sequence of processes with a given length. By
sequence it is meant that each created process has exactly one child.
Let's look at some example outputs for the program.
Here the entire process sequence consists of process 18181:
Sara@dell:~/OSSS$ ./linear 1
Creating process sequence of length 1.
18181 begins the sequence.
An example for a sequence of length three:
Sara@dell:~/OSSS$ ./linear 3
Creating process sequence of length 3.
18233 begins the sequence.
18234 is child of 18233
18235 is child of 18234


........ this is coad .... BUt i could not compleate it .....http://im.cprogramming.com/images/smilies/frown.png
Code:

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {

int N;
pid_t pid;

int cont;

if (argc != 2) {
printf("Wrong number of command-line parameters!\n");
return 1;
}

N = atoi(argv[1]);

printf("Creating process sequence of length %d.\n",N);

printf("%d begins the sequence.\n",getpid());

/* What I have to do next ?????? */

}

[anduril462]

You need to use the fork function with a simple loop. Type "man fork" from your command line for the documentation on the function, and Google for some examples. Here's one site to get you started: Introduction to C/Unix Multiprocess Programming - Fork and Exec - We'll just go through some very simple example code, to see how to use fork() and execl()..

[zooro]

what is wrong ....?!!!
i dont get right ....any hints??

 #include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {

int N;
pid_t pid;

int cont;

if (argc != 2) {
printf("Wrong number of command-line parameters!\n");
return 1;
}

N = atoi(argv[1]);

printf("Creating process sequence of length %d.\n",N);

printf("%d begins the sequence.\n",getpid());

/* What I have to do next ?????? */
 for(cont=0;cont<N;cont++)

 {
 if(fork() == 0){
 
printf("%d is child of %d \n",getpid(),getppid());
 }
 }
 
}

[anduril462]

Fix your indentation, it's horrible. Clear, readable code is an imperative, especially when working with others, like you are doing on this forum. If you don't have a style you like yet, I recommend one of the first 3 styles mentioned here: Indent style - Wikipedia, the free encyclopedia. They're widely used in the C world.

Then, you need to work on providing a clear description of what is wrong. Does this code compile? If not, post the exact error messages with line numbers (copy-paste the compiler output). If it does compile, do you get no output or the wrong output? Provide the incorrect output. Does it crash?

[oogabooga]

One problem is that both the child AND the parent are going to keep looping, but you don't want the parent to continue looping. You want the parent to break out of the loop and then wait for its child.

[zooro]

Here what I should get if I enter the following

(An example for a sequence of length three):

Sara@dell:~/OSSS$ gcc –o file file.c
Sara@dell:~/OSSS$ ./file 3
Creating process sequence of length 3.
18233 begins the sequence.
18234 is child of 18233
18235 is child of 18234


Now I am getting the following :
Sara@dell:~/OSSS$ gcc –o file file.c
Sara@dell:~/OSSS$ ./file3
Creating process sequence of length 3.
13324 begins the sequence.
Sara@dell:~/OSSS$ 13327is child of 1.
13326is child of 1.
13325is child of 1.
13330is child of 1.
13328is child of 1.
13329is child of 1.
13331is child of 1.
Sara@dell:~/OSSS$

[oogabooga]

Well, post your code ... and remember to break out of the loop if it's the parent (if the return value of fork() is not 0).

[zooro]

Thank u oogabooga http://im.cprogramming.com/images/st...ser-online.png
i did not get your point ...why I breack out the loop??!!

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {
 
int N;
pid_t pid;
 
int cont;
 
if (argc != 2) {
printf("Wrong number of command-line parameters!\n");
return 1;
}
 
N = atoi(argv[1]);
 

printf("Creating process sequence of length %d.\n",N);
 
printf("%d begins the sequence.\n",getpid());
 
/* What I have to do next ?????? */
 for(cont=0;cont<N;cont++)
 
 {
 if(fork() == 0){
  
printf("%d is child of %d \n",getpid(),getppid());
 }
 }
  
}

[anduril462]

Also, remember your other thread (here fork ()), where I told you to read up on the wait() funciton? Well, do that, and pay particular attention to the "NOTES" section, it will explain why it says "child process of 1".

As for why you break out of the loop, you must remember, after a call to fork, there is both a parent and a child process that are at the exact same spot in execution.

[oogabooga]

i did not get your point ...why I breack out the loop??!!

I didn't say to "breack" out of anything. I don't even know what that means. If you're not even going to try, then forget it.

[zooro]

I Got it ..... it were fork the parent every time where it should fork the child.......Here the right coad ......

#include <stdio.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include <stdlib.h>
 
 int main (int argc, char *argv[])
 {
 int N;
 pid_t pid,child_pid;
 int cont;
 
 if (argc !=2)
 {
 printf("Wrong number of command-line parameters!\n");
 return 1;
 }
 
 N = atoi (argv[1]);
 printf("Creating process sequence of length %d.\n", N);
 printf("%d begins the sequence.\n",getpid());
 
 
 
 
 child_pid= fork();
 for (cont =0 ; cont<N-1; cont++)
 {
 
 pid=getpid();
 
 if ( child_pid==0)
 {
 
 printf("%dis child of %d.\n", getpid(),getppid());
 child_pid=fork();
 }
 wait();
 
 }
 }