I want to write a program in Linux which by getting a session id could print all processes and process groups in that session in a tree view structure!?
How can I extract such information!? Should I resort to proc file system?
Most (all?) Linux programs read /proc to know about running processes.
If you are using Perl, then may be Proc::ProcessTable cpan module may save you some work.
Edit: Since you are using C, then you can look at pstree source code to get inspiration.