UNIX for Dummies Questions & Answers

as the kernal invokes a process INIT during the time of booting which in turn spawns all other processes because of which it is considered as parent process.

does it too calls system call fork() or there is something like this?

init() process2()

{
{ process3()
process2;
} } and so onnnnnnnnnnnnnn.


please dont mind if you think it a stupid question.because i am a student learning UNIX i want to know the UBDERLYING CONCEPTS and NOT JUST COMMANDS.


THANKS amor1

You welcome, and there're no stupid questions, we learn sofisticated system with some 30+ years of development...

Generally as far as I learned there are only two ways for making unix process and here they are:
1. The special processes: these are processes that are created under system boot time and they are created by some programing tricks and special methods, it is not UNIX yet, it is a midway. Depending of version of unix it is may be just init process or there are may be two-three with some memory-disk swapping "abnormal" deamon that system will not let you kill.

2. The normal processes: as we desribed above, and ALL the processes use the same scheme. It allows in a turn to command processes in a similar way, by sending signals to them (you always can get a list of signals available for your system with "kill -l" command). It also implyes the so called "standard process lifespan".

Generally speaking, yes all processes including init use the same scheme for replicating, by the end of their lifespan, process passes so called "zombi" phase and thankfully to the scheme, init takes care to remove the proceses that had not been removed properly by their own parent processes (in a case when parent process was terminated before child process).
Hope it helps.

thanks for your encouragement amro1.


as you told earlier a commnand kicks of other process which does the job on its behalf.

do all commands CREATE child process?
if not how can i say EXACTLY which one CREATES A CHILD and WHICH DOES NOT

is there any criteria to decide upon?

Why should it create and what is the need for that?
Did you mean command or system call ?

One go would be,
processing service requests where parent would handle incoming requests alone, forks and handover the processing job to the child and parent would block on listen-for active requests.

let us say ,we have two commands

cat file1, vi file2

is it possible to judge which of these two commands will kick off a child process?

if it is possible in any means like through programming or any other means to say EXACTLY which commands create child process which does not let me know.

this is what exactly i wanna knkow

thanks

you can judge on the basis of functionality , and if you need to know for sure, for each systems there is process descriptor in /proc. Look into system specific manual to interpret the data in /proc.