forking n number of processes in a loop and not 2^n - High Level Programming

rvan · #1 01-09-2007

Hi,

Am working on linux. while forking in a loop how to avoid the child process from forking..for example

int n = 5;
pid_t pid;
pid_t ch_pid[5];

/*exactly wanted to create n processes and not 2^n processes*/

for(i = 0; i < n;i++)
{
if(pid = fork())
{
/* parent process */
ch_pid[n] = pid;
waitpid(pid);
}
else if(pid == 0)
{
/*child process*/
spawn_process(ch_pid[n], n);
/*In spawn_process() i will call exec()*/
}
else
{
/*Handle error*/
}
}
1. Once the child process calls exec(), do I need to do something to restrict the child process from forking?

2. What will be the stack size allocated for the child processes?

Thanks,
Anand

rvan · #2 01-09-2007

Hi,

Am working on linux. while forking in a loop how to avoid the child process from forking..for example

int n = 5;
pid_t pid;
pid_t ch_pid[5];

/*exactly wanted to create n processes and not 2^n processes*/

for(i = 0; i < n;i++)
{
if(pid = fork())
{
/* parent process */
ch_pid[n] = pid;
waitpid(pid);
}
else if(pid == 0)
{
/*child process*/
spawn_process(ch_pid[n], n);
/*In spawn_process() i will call exec()*/
}
else
{
/*Handle error*/
}
}
1. Once the child process calls exec(), do I need to do something to restrict the child process from forking?

2. What will be the stack size allocated for the child processes?

Thanks,
Anand

jim mcnamara · #3 01-10-2007

This is how to control the number of children. I'll let you work out calling execl()

Code:

#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>

int foo(const char *whoami)
{
	printf("I am a %s.  My pid is:%d  my ppid is %d\n",
			whoami, getpid(), getppid() );
	return 1;
}

int main(int argc, char **argv)
{
	int n=atoi(argv[1]);
	int i=0;
	int status=0;

	if (n==0) n=2;
	printf("Creating %d children\n", n);
	foo("parent");
	for(i=0;i<n;i++)
	{
		pid_t pid=fork();
		if (pid==0) /* only execute this if child */
		{
			foo("child");
			exit(0);
		}
		wait(&status);  /* only the parent waits */
	}
	return 0;
}

elzalem · #4 01-10-2007

to prevent the child from spawning another child, kill that child before it loops!
in other words,don't ever let it loop the for( ; ; ), or add if (pid !=0 ) before the fork () call

rvan · #5 01-17-2007

Hi guys ,

thnk u for ur help
i don't want to kill the child processess
"if (pid !=0 )" helped me a lot..
thnk u once again..

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