#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>

const char *commands[] = {
        "quit", "who", "ls", "uptime", "emacs", "hostname", "date", ""
};

void print_menu( void )
{
        int i;
        printf( "Enter" );
        for ( i = 0; commands[ i ][ 0 ]; ++i )
                printf( " %d=>%s", i, commands[ i ] );
        printf( "-> " );
}

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 ); 
                        if ( cmd == 4 )
                                execl( "/usr/bin/emacs",
                                       "emacs", NULL ); 
                        if ( cmd == 5 )
                                execl( "/bin/hostname",
                                       "uptime", NULL ); 
                        if ( cmd == 6 )
                                execl( "/bin/date",
                                       "uptime", NULL );
                        printf( "command %d not supported\n", cmd );
                        exit( 1 ); 
                }
                wait( NULL );
                print_menu();
                scanf( "%d", &cmd );
        }
}