can anyone tell me the program about how to implement a routine similar to getpid() in C program without using the function getpid(). ie. the program has to find out the pid of the process without using the getpid command. Please do help me in this regards at the earliest.

Where I come from, getpid() is a system call. Anything that gets it is going to be using getpid() to do so, eventually; there's nothing below it to use.

If a simply less direct method will do, check if you've got /proc/self on your system -- it'll be a symlink to /proc/<pid#>

This is the Solaris 10 implementation of the getpid system call.

Maybe you could pick up some leads from there?

You can also fork() and read the result of getppid() from the child or raise() a signal with SA_SIGINFO set and examine si_pid or use msgsnd() and look at msg_lspid for the message queue or send PID data through some other platform-specific IPC addons, such as process credentials transferred thru STREAMS or Unix domain sockets. There are probably many more ways.