$(echo $RANDOM | cut -b 1-2) returns empty line in a shell script

Question

I have this script,

#!/bin/sh
guess=$(echo $RANDOM | cut -b 1-2)

read -p "Im thinking of a number, can you guess what it is? " number

case "$number" in
    "$guess") echo "\nCongratulation number guessed corectly!"
        exit 0
        ;;
    *) echo "\nIncorrect number guessed, try again? [yes or no]"
        read yesorno
        case "$yesorno" in
            "yes") sh guess.sh
                ;;
            "no") echo "\nHave a nice day!"
                exit 0
                ;;
            *) echo "Invalid input"
                exit 1
                ;;
        esac
        ;;
esac

The variable $guess was suppossed to return a 2 digit number, but returns null. Running the game with sh guess.sh and pressing return, returns congrats instead of the correct number being guessed. Where am I going wrong

Does this answer your question? [Random number generation in Solaris?](https://unix.stackexchange.com/questions/245036/random-number-generation-in-solaris) — muru, Dec 29 '20 at 19:43

score 5 · Accepted Answer · answered Dec 29 '20 at 19:42

5

Use bash instead of sh

guess=$(echo $RANDOM | cut -b 1-2)
             ^-----^ SC3028: In POSIX sh, RANDOM is undefined.

answered Dec 29 '20 at 19:42

Rabin

3,818
1
21
23

1

`read -p` is furthermore not guaranteed to work in non-bash scripts. You may also want to comment on the way they run the script recursively... – Kusalananda Dec 29 '20 at 19:51
Running this with ./guess.sh(provided that declare #!/bin/bash) runs fine, however, sh guess.sh shows faulty result. – atheros Dec 29 '20 at 19:52
That because you overwrite the shell which execute the script – Rabin Dec 29 '20 at 19:53
Okay, I'm upvoting both of the answers, Adding #!/bin/bash solved the issue, if ran with ./guess.sh. – atheros Dec 29 '20 at 19:56

score 2 · Answer 2 · answered Dec 29 '20 at 19:40

2

The -b flag in cut is for bytes, try the -c flag for characters instead.

I would also suggest changing the shebang to #!/bin/bash or #!/usr/bin/env bash. Otherwise it will use the system default (on Ubuntu this is dash) using POSIX mode.

answered Dec 29 '20 at 19:40

shiftF5

21
2

$(echo $RANDOM | cut -b 1-2) returns empty line in a shell script

2 Answers2