On Wed, 2006-05-31 at 14:01 +0100, Ashok Sharma wrote: > --- Taha Hafeez Siddiqi <tawushafeez@xxxxxxxxx> wrote: > > > On Tue, 2006-05-30 at 14:33 +0100, Ashok Sharma > > wrote: > > > Here is a related question. > > > When I fork() from a process a parent process with > > > some id is created together with a child process > > with > > > pid same a id of parent and id (of child) is zero. > > > > > > (Please correct me if I am wrong or partially > > right:) ) > > fork() system calls return twice from the kernel, > > once it returns for > > the parent and in this case fork has a return value > > as the pid of the > > child as there is no other way for the parent to get > > the pid of the > > child. > > > > The second return is for a new child (having > > different pid ofcourse). > > Here the return value is 0. It doesn't need the pid > > of the parent as it > > Yes pid of child is same as id of parent and id of > child is zero. > > Now if child forks() then grandchilds pid and id will > be what values? As id of child and pid of grandchild > must be same? Or does id of child change? > > Best > Ashok Hi .... There seems to be a confusion. What do you mean by id? and believe me Ashok, if you mean "id" is "pid", then you need to explore linux/unix more before taking on the kernel. Check out the basic unix books e.g. "The Unix programming environment" by Kenighan-Pike. "Advanced Unix Programming" by Richard Stevens. regards Taha > > can easily get that using getppid() call. > > > > So, each process(child and parent) has its own pid > > and what you are > > confusing as pid is only the return value. > > > > > > > > Now if from a child I fork() again then what will > > be > > > the pid and id of the child (or grand child) now. > > Both > > > cannot be zero again and what happens if I fork > > again > > > from the grand child? > > > > > > Pl. clear my doubt > > > > > This, I suppose, stands cleared now.... > > > > > > > > > Cheers > > > ashok > > > > > > > > > > Hope this helps.... > > Taha > > > > > > > > > > > > > > > > > --- Gopala Krishna <gopalakrishna.n.m@xxxxxxxxx> > > > wrote: > > > > > > > > > > > > > Fortunately, here comes the proc filesystem ! > > > > > So, you have the pid of the father process : > > look > > > > at the file > > > > > /proc/'ppid'/status there should be a fild > > ppid : > > > > you have the pid of > > > > > your grand parent. > > > > > You can do a recursive function to find all > > the > > > > ancestors of your > > > > > process. > > > > > This solution is quite annoying since you have > > to > > > > handle files, but it > > > > > works. > > > > > > > > > > If this solution is not acceptable for you, > > you > > > > can look at the pstree > > > > > source code. > > > > > > > > > > I don't know if you wanted to do that in your > > own > > > > programm or just > > > > > wanted some soft to give you the entire tree > > (like > > > > pstree). Anyway... : > > > > > > > > > > > > > > > > In My case, I knew only pid of the first > > process. I > > > > want the top down > > > > approach rather than the bottom up (i.e if I > > know > > > > child, I know parent. but, > > > > my requirement is to find out child and it's > > grand > > > > children, If I know the > > > > parent pid). Currently I am going through pstree > > > > code. > > > > > > > > Thanks and regards, > > > > Gopal. > > > > > > > > > > > > > > > > > > > > > > > > > > > > ___________________________________________________________ > > > > > Win tickets to the 2006 FIFA World Cup Germany > > with Yahoo! Messenger. > > http://advision.webevents.yahoo.com/fifaworldcup_uk/ > > > > > > -- > > > Kernelnewbies: Help each other learn about the > > Linux kernel. > > > Archive: > > http://mail.nl.linux.org/kernelnewbies/ > > > FAQ: http://kernelnewbies.org/faq/ > > > > > > > > > -- > > Kernelnewbies: Help each other learn about the Linux > > kernel. > > Archive: > > http://mail.nl.linux.org/kernelnewbies/ > > FAQ: http://kernelnewbies.org/faq/ > > > > > > > Send instant messages to your online friends http://uk.messenger.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
