RE: [LIP] fork()...

thanks Uday.

> So that you could determine whether you are in the child or the parent
> process.

> if (!fork ()) {
> 	/* this is the code that the child is supposed to run, use getpid to
> get the process id */
> 	/* you would proabably want to exec something here */
> }
> /* parent code runs here */

> At fork a new child process is created with exactly the same process image
> as the parent, now the only way to tell whether you are a child or parent
> process is by examining the return code from fork.
...
this reason is known to me.
i think there're few more.

these are the reasons what i think:
1> fork() returns -1 with errno set to EAGAIN(violating the upper limit of
processes user can create, if UID is not 0)
or ENOMEM(if not sufficient memory for the new process to have it's bss,
text and other data)if it was not successful.
0 or some +ve value are returned if fork() was successful. 0 also indicates
a success as almost all system calls do.
i guess this's one of the reasons.

2> also, the other reason is there're processes with PID starting from 1.
almost all UNIX systems
have 1 for init(some systems have 2 for page-daemon). the scheduler is not
given any no, since it's initially init 0
and after spawning init(what is also known as init 1), it becomes scheduler.
since there's no process with PID 0 existing, 0 can safely be used to
indicate the success status of
the fork() system call along with the PID of the newly created child.

any comments???


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