Unix identifies each process with a unique integer called ProcessID. The process
that executes the request for creation of a process is called the 'parent process'
whose PID is 'Parent Process ID'. Every process is associated with a particular
user called the 'owner' who has privileges over the process. The identification
for the user is 'UserID'. Owner is the user who executes the process.
Process also has 'Effective User ID' which determines the access privileges
for accessing resources like files.
getpid() -process id
getppid() -parent process id
getuid() -user id
geteuid() -effective user id