CODEWITHSUNDEEP
bash
Dave55
Dave55

Reputation: 13

Loading a while true loop into a variable

I'm having a bit of trouble getting this to work/ knowing if its possible. I'm creating a game using little other than bash, this requires a lot of repeated case statements. I am trying to load all the repeated case statements into a variable, then repeat them when necessary to limit the amount of work it will take to update the shared case statements between different scripts. Here is what I have: 

#!/bin/bash

moo="[m][o][o]) echo 'thank you for following instructions' ;;"

test=$(echo "while true ; do
read -p 'type moo: ' case
case $case in
$moo
*) echo 'type moo please'
esac
done")

"$test"

The problem I run into is:

./case.sh: line 13: $'while true ; do\nread -p \'type moo: \' case\ncase  in\n[m][o][o]) echo \'thank you for following instructions\' ;;\n*) echo \'type moo please\' ;;\nesac\ndone': command not found

The information in the moo variable will eventually be in a separate script and will be set by invoking it as a function within that script when I finally get a working model. It looks like this is a workable idea, I've just reached a loss on how to invoke the variable without it acting up. If anyone has any ideas, I would greatly appreciate it. Thank you in advance!

Upvotes: 1

Views: 56

Answers (1)

Barmar
Barmar

Reputation: 780974

It doesn't work because the quotes make the variable expansion be treated as a single word.

But it wouldn't work without quotes, either, because the shell doesn't parse the output of variables for syntax like semicolon and newline. Variable expansion is done after that stage of command parsing. The only processing that's done on expanded variables is word-splitting and wildcard matching.

You need to use eval to perform all command parsing:

eval "$test"

Another problem is that the variable $case is being expanded when you assign the variable test, it's not getting the value being read by read. Since the variable doesn't have a value yet, it's being executed as:

case in ...

and this is invalid syntax. You need to escape the $ so it will be passed through literally.

There's also no need for echo, you can simply assign the string directly.

test="while true ; do
read -p 'type moo: ' case
case \$case in
$moo
*) echo 'type moo please'
esac
done"

Upvotes: 1

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