awk Rock-Paper-Scissors

Rock-Paper-Scissors

Rock-paper-scissors is a popular hand game in which each player simultaneously forms one of three shapes with an outstretched hand. We create this game in AWK.

# This program creates a rock-paper-scissors game.

BEGIN {

    srand()
    
    opts[1] = "rock"
    opts[2] = "paper"
    opts[3] = "scissors"

    do {
    
        print "1 - rock"
        print "2 - paper"
        print "3 - scissors"
        print "9 - end game"
        
        ret = getline < "-"

        if (ret == 0 || ret == -1) {
            exit
        }
        
        val = $0
        
        if (val == 9) {
            exit
        } else if (val != 1 && val != 2 && val != 3) {
            print "Invalid option"
            continue
        } else {
            play_game(val)
        }
    
    } while (1)
}

function play_game(val) {

    r = int(rand()*3) + 1

    print "I have " opts[r] " you have "  opts[val]
    
    if (val == r) {
        print "Tie, next throw"
        return
    }
    
    if (val == 1 && r == 2) {
    
        print "Paper covers rock, you loose"
    } else if (val == 2 && r == 1) {
    
        print "Paper covers rock, you win"
    } else if (val == 2 && r == 3) {
    
        print "Scissors cut paper, you loose"
    } else if (val == 3 && r == 2) {
    
        print "Scissors cut paper, you win"
    } else if (val == 3 && r == 1) {
    
        print "Rock blunts scissors, you loose"
    } else if (val == 1 && r == 3) {
    
        print "Rock blunts scissors, you win"
    } 
}

We play the game against the computer, which chooses its options randomly.

srand()

We seed the random number generator with the srand() function.

opts[1] = "rock"
opts[2] = "paper"
opts[3] = "scissors"

The three options are stored in the opts array.

do {

    print "1 - rock"
    print "2 - paper"
    print "3 - scissors"
    print "9 - end game"
...    

The cycle of the game is controlled by the do-while loop. First, the options are printed to the terminal.

ret = getline < "-"

if (ret == 0 || ret == -1) {
    exit
}

val = $0

A value, our choice, is read from the command line using the getline command; the value is stored in the val variable.

if (val == 9) {
    exit
} else if (val != 1 && val != 2 && val != 3) {
    print "Invalid option"
    continue
} else {
    play_game(val)
}

We exit the program if we choose option 9. If the value is outside the printed menu options, we print an error message and start a new loop with the continue command. If we have choosen one of the three options correctly, we call the play_game() function.

r = int(rand()*3) + 1

A random value from 1..3 is chosen with the rand() function. This is the choice of the computer.

if (val == r) {
    print "Tie, next throw"
    return
}

In case both players choose the same option there is a tie. We return from the function and a new loop is started.

if (val == 1 && r == 2) {

    print "Paper covers rock, you loose"
} else if (val == 2 && r == 1) {
...

We compare the chosen values of the players and print the result to the console.

$ awk -f rock_scissors_paper.awk 
1 - rock
2 - paper
3 - scissors
9 - end game
1
I have scissors you have rock
Rock blunts scissors, you win
1 - rock
2 - paper
3 - scissors
9 - end game
3
I have paper you have scissors
Scissors cut paper, you win
1 - rock
2 - paper
3 - scissors
9 - end game

A sample run of the game.