in the heading list in ps -l, what do WCHAN, SZ, ADDR, NI, PRI, and C mean?? like the way F means for process flags...
Can someone plz explain the concept of "time slicing" with relation to the kernal scheduler??

in a program where you give 2 fork() commands, why is it important to have sleep command?? if u exclude the sleep command you get funny output..
////
main()
{
fork();
fork();
printf("parent pid %d\n", getppid());
sleep(3);
}
//////

man ps and page down to the description of the headings...

Time Slice, and follow the link to multi tasking

What is the funny output that you get?

the output that i get with the sleep command is
parent pid 3947
parent pid 3946
parent pid 3946
parent pid 2699

the output that i get without the sleep command is..
parent pid 3947
parent pid 3946
[XXX @localhost]parent pid 1
parent pid 1 (with the curser blinking continuously at this point)

pid 1
is the init process.

congratulations kid, you've created a Zombie!

as you are playing with forks;
you should become very familiar with the pkill command.
you may need it.

With zombie processes you want to handle them with a waitpid signal handler on the SIGCHLD signal. Which may sound like a lot of gobbledegook however it should give you sufficient information to do an effective goggle and make some sense of it .

As for your code the standard approach is to look at the return from fork. If it is zero then you are in the parent process, if it is non zero then you are in the child process and the value returned is the pid of the parent. The reason you have four values displayed is there is first of all the parent, then the parent creates a child (1st fork) then the 1st child and the parent create a child each (2nd fork), giving you a total of four children. If you check that you are in the parent process before forking then you will create a total of two children and one parent.

I hope that helps,

graeme.