| 1 | #!/bin/sh
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| 2 |
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| 3 | # Instead of using if, elif, elif, elif, else, there's a more concise
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| 4 | # (and often faster) method you can use; case.
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| 5 | #
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| 6 | # $ echo "Enter a letter: "
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| 7 | # $ read user_input
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| 8 | # $
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| 9 | # $ case "$user_input" in
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| 10 | # $ [a-z])
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| 11 | # $ echo "Entered: lowercase"
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| 12 | # $ ;;
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| 13 | # $ [A-Z])
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| 14 | # $ echo "Entered: uppercase"
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| 15 | # $ ;;
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| 16 | # $ [0-9])
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| 17 | # $ echo "I said letter, not number"
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| 18 | # $ ;;
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| 19 | # $ *) # for everything else
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| 20 | # $ echo "What?"
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| 21 | # $ ;;
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| 22 | # $ esac
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| 23 | #
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| 24 | # The snippet above should be self explanatory. Now, for other cases, it
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| 25 | # can look like this
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| 26 | #
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| 27 | # $ case "$item" in
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| 28 | # $ apple|banana|orange) # apple or banana or orange
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| 29 | # $ echo "Food item"
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| 30 | # $ ;;
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| 31 | # $ book)
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| 32 | # $ echo "leisure item"
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| 33 | # $ ;;
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| 34 | # $ *)
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| 35 | # $ echo "unknown"
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| 36 | # $ ;;
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| 37 | # $ esac
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| 38 | #
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| 39 | # It's better to use 'case' instead of 'if' when you are pattern
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| 40 | # matching, which means you can avoid using grep. It can be better to
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| 41 | # do 'if' instead of 'case' when there's arithmetic, like playing a
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| 42 | # hotter/colder game by having a user try to find a number.
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| 43 | #
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| 44 | # Below is the unfinished work of a rock-paper-scissors game between
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| 45 | # a player and the computer
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| 46 |
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| 47 | choices="rock paper scissors"
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| 48 | computer_choice=$(echo "$choices" | tr ' ' '\n' | shuf -n 1)
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| 49 | printf "Choose rock paper or scissors: "
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| 50 | read player_choice
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| 51 |
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| 52 | # The code snippet above needs no changing.
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| 53 | # Have all the echo statements be just those 3 words exactly
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| 54 | # Error messages can be helpful here
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| 55 | case "$player_choice" in
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| 56 | rock)
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| 57 | case "$computer_choice" in
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| 58 | rock) echo "tie" ;; # this is a valid way of condensing code
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| 59 | paper) echo "lost" ;;
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| 60 | scissors) echo "won" ;;
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| 61 | *)
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| 62 | echo "ERROR invalid option"
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| 63 | ;;
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| 64 | esac
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