help in C of fork() problem


 
Thread Tools Search this Thread
Top Forums Programming help in C of fork() problem
# 1  
Old 02-25-2011
help in C of fork() problem

i am a beginner of C, and i tired to fork multiple child and all of them belongs to same parents and each of child responsible for printing individual data.
but i don't have any idea how to do......
Can any body help? thanks a lot really.

Last edited by wendy1089; 02-25-2011 at 04:09 PM..
# 2  
Old 02-25-2011
What have you tried?
# 3  
Old 02-25-2011
I have tried using for loop to create multiple childs
and when using pid==0 and the child process to output the data, but how to set the data for different child and how to make them print out each individual data?
# 4  
Old 02-25-2011
Each child gets its own copy of the parent's variables. You can use the value of the for-loop to tell which child it is. Substitute your actual variable for 'n'.

Code:
if(pid == 0)
{
        fprintf(stderr, "This is child %d\n", n);

        switch(n)
        {
        case 0:
                fprintf(stderr, "This happens only in child zero\n");
                break;
        case 3:
                fprintf(stderr, "This happens only in child three\n);
                break;

        default:
                fprintf(stderr, "Any other child just runs this\n");
                break;
        }

        exit(0); // So you don't accidentally continue the for-loop in the child
}

# 5  
Old 02-25-2011
i got what u mean. i am trying now. i hope it can be success.
thank you very much really.

---------- Post updated at 03:43 PM ---------- Previous update was at 03:39 PM ----------

by the way, this is my orginally program to fork(). but why it can't print out the child number although i use child++ ??
Code:
#include <stdio.h>  
#include<stdlib.h>
int main()
{
int parent=0, child=0, i=0, result, pid;
 pid = fork(); /* creates a new process, you only want the parent to spawn children? */
  for (i; i < 20; i++)
  {
	switch (pid)
   {
		 case -1:
			/* fork error */
			printf("Error occoured with fork()\n");
			exit(99);
		 case 0:
			/* child process */
			printf("child %d %d %d\n",getpid(), child++,getppid()); exit(0); 
		 default:
			 /* parent process*/
			{
			printf("parent %d %d\n", parent++, child);
			pid = fork(); /* fork new children here */
			wait();
			}
   }
  }
}


Last edited by Franklin52; 02-26-2011 at 07:55 AM.. Reason: Please use code tags
# 6  
Old 02-25-2011
Quote:
Originally Posted by wendy1089
by the way, this is my orginally program to fork(). but why it can't print out the child number although i use child++ ??
Each child gets its own independent "child" variable containing the value it had in the parent: Zero. Variables aren't shared, just copied. Each child also gets an independent copy of i, which will be 0 in the first child, 1 in the second child, etc, etc. because that's the value it had when the parent called fork().
# 7  
Old 02-26-2011
i still have some difficulties about the program.
in fact, i want to use argv allow user to input n children what they want, and many numbers (which need to sort and let child to count how many value numbers they got later).

but i want ask after creating fork(),
how can i pass the argv value from parent to children, i want first child to read argv first number and second child read second,etc. how can i do that?
i hope some one can give me some idea how to do that.

---------- Post updated at 10:59 AM ---------- Previous update was at 02:57 AM ----------

also how to save pid into array? i tried to use int for it data type, but it seems not successful.
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

Very basic problem with fork() using c

Hi guys, I have the following code: int main(int argc, char *argv) { int pid1,pid2,i=0; pid1=fork(); i+=2; if(!pid1) i++; if(i%3) pid2=fork(); if (pid2==0) { printf("sea \n "); i-=1; } if(i>=2)... (4 Replies)
Discussion started by: pfpietro
4 Replies

2. UNIX for Dummies Questions & Answers

Problem with fork() while reading files

Good evening everyone. I have my finals and I'm facing a problem: I have a for cycle that is supposed to fork 2 children but somehow it forks only the first one. What am I doing wrong ? #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h>... (1 Reply)
Discussion started by: pfpietro
1 Replies

3. Programming

Problem with fork() and execlp process

Hello everyone, this is my first post. I have a task to use a fork to create multiple processes and then use execlp to run another program to add 2 numbers. The problem I am having is we are supposed to use the exit() call in the execlp to return the small integer. This is a bad way to... (3 Replies)
Discussion started by: Johnathan_1017
3 Replies

4. Programming

problem with mutltiple fork()

Hi, can someone please help me with creating mutltiple fork.. I was expecting something like this: I am a child: 1 PID: 1215 I am a child: 2 PID: 1216 I am a child: 3 PID: 1217 I am a child: 4 PID: 1218 I am a child: 5 PID: 1219 I am a child: 6 PID: 1215 I am a child: 7 PID: 1216 I am a... (4 Replies)
Discussion started by: Placenzo
4 Replies

5. Programming

Fork and then exec problem with signals

Hi All, In my program i am handling SIGHUP signal. In the handler i fork and then exec on child process same binary file which is running. Parent process will die after 10 mins. Now my child process which was exec with same binary file is not receiving SIGHUP signal. Below is the progran code:... (6 Replies)
Discussion started by: sushil_shalin
6 Replies

6. UNIX for Dummies Questions & Answers

simple fork() problem

I have this little program ... int main(void){ printf("Before"); fork(); printf("After"); } output is this..... BeforeAfterBeforeAfter Shouldnt it be.....BeforeAfterAfter After parent is forked child receives the copy of program and continues from next statement... (3 Replies)
Discussion started by: joker40
3 Replies

7. Programming

problem implementing fork

Hi, I was honing my linux programming skill when this nuisance started bugging me. I wanted to create an empty file creator program. While creating a large file it must print # for progress bar. But the output shows it happening reverse way. ie. first it copies file and shows the progress... (7 Replies)
Discussion started by: dheerajsuthar
7 Replies

8. UNIX for Advanced & Expert Users

Problem due to Fork Error

Hi, I have developed a datastage job...which has many process running in parallel..but because of Fork Error my job is not working:( Can any body help me out to solve this Fork error problem.:rolleyes: My Os is SUNOS. IS there any setting in Unix through admin where in if i set some paramter... (8 Replies)
Discussion started by: Amey Joshi
8 Replies

9. Programming

fork() problem

i'm just trying to make 2 process read from the same 1 line a time. For some reason only the child reads. #include<stdio.h> #include <sys/types.h> void getlinefromfilep(void); void getlinefromfilec(void); int see=0; FILE * fileptr1; //need globe variable to tell pro3 to stop main()... (3 Replies)
Discussion started by: ddx08
3 Replies

10. Programming

fork problem

Hi, Consider the following piece of code: int main(void) { int i; pid_t pidp; for (i=0;i<4;i++) { switch (pidp=fork()) { case -1: fprintf(stdout, "Error during fork.\n"); exit (1); case 0: fprintf(stdout, "From child: I am... (4 Replies)
Discussion started by: qntmteleporter
4 Replies
Login or Register to Ask a Question