#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
 

int 
main()
{
        pid_t  pid;
        int    id, ecode;

        pid = getpid();
        printf( "[%d] main process before fork() call.\n", pid);
         
        id=fork();
        if( id>0 )
        {
                /* parent process */
                printf( "[%d] main process after fork() call, created child process with id=%d.\n", pid, id );
                wait( &ecode );   /* % 0xFF for ignoring effect of possible SIGCHLD signal at the end of child */
                printf( "[%d] child[%d] process finished with exit code %d.\n", pid, id, ecode % 0xFF);
        }
        else if( id==0 )
        {
                /* child process */
                pid = getpid();
                printf( "[%d] inside child process of parent[%d].\n", pid, getppid() );
                exit( 3 ); /* just sample value */
        }
        else
        {
                /* fork creation error */
                fprintf( stderr, "[%d] error: fork() failed.\n", pid );
        }
        return 0;
}