C :: Program To Check For Running Pid Using System Call In UNIX / Linux

I have written a program which uses a pid to check if the process is currently running and return a value based on the system call result.But the program core dumps

Code:

#include <stdio.h>
#include <string.h
int main( argc, argv )
int argc;
char * argv[];
{
int p_pid = 99;
char buff[1000];
}

[code]....

What is the mistake in this code and is it portable in both unix/linux , is the method secure (grepping for program name )?