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

void print_menu( void )
{
       printf( "Enter 1=who, 2=ls, 3=uptime -> " );
}

int main()
{
        int cmd; 
        print_menu();
        scanf( "%d", &cmd );
        while ( cmd != 0 ) { 
                int pid = fork(); 
                if ( pid == 0 ) { 
                        if ( cmd == 1 )
                                execl( "/usr/bin/who",
                                       "who", NULL ); 
                        if ( cmd == 2 )
                                execl( "/bin/ls", 
                                       "ls", NULL ); 
                        if ( cmd == 3 )
                                execl( "/usr/bin/uptime",
                                       "uptime", NULL ); 
                        exit( 1 ); 
                }
                /* add: wait( NULL ); here */
                print_menu();
                scanf( "%d", &cmd );
        }
}