Loop until choice within list - linux

Question

I am trying to write a script which loops until the user chooses a value within a list (single digit numbers from 0 to 9). This is my .sh script which I try to run in the ubuntu 16.04 shell using the sh command:
choice=999
echo $choice
until [[ $choice in 0 1 2 3 4 5 6 7 8 9 ]]
do
read -p "How many would you like to add? " choice
done
No matter what I do, I just can't get it to work. Here's a test, to give you an idea of the errors at hand:
sh test2.sh
999
test2.sh: 3: test2.sh: [[: not found
How many would you like to add? f
test2.sh: 3: test2.sh: [[: not found
How many would you like to add? 2
test2.sh: 3: test2.sh: [[: not found
How many would you like to add? 3
test2.sh: 3: test2.sh: [[: not found
How many would you like to add? r
test2.sh: 3: test2.sh: [[: not found
I've tried so many things:
Avoiding until and using while
Using just singular square brackets [ condition ], or no brackets at all
Using =~ to match the regular expression ^[0-9]
Nothing works. Always that same error. What's going on? :(

Answer 1

Firstly, your [[: not found suggests that you're not using Bash. Either add a #!/bin/bash at the top of your script, or run it with bash test2.sh, or use the standard [.
Either way, you can't use in like that. One alternative would be to use a case statement:
while :; do
read -p "How many would you like to add? " choice
case $choice in
[0-9])
break
;;
esac
done
The nice thing about case statements is that they allow you to use glob patterns, so [0-9] matches any number from 0 to 9.
If you are planning on using Bash in the end, you can also go for something like this:
#!/bin/bash
until [[ $choice =~ ^[0-9]$ ]]; do
read -p "How many would you like to add? " choice
done
Here, a regular expression is used to match a since digit from 0 to 9.

Answer 2

[[: not found is bash builtin, not sh.
Can you check your she-bang and be sure that it's #!/binb/bash, not #!/bin/sh ? And the second, run script as bash scriptname.sh, not with sh.
And finally, try to rewrite your script like that:
choice=999
echo $choice
while [[ "$(seq 0 9)" =~ "${choice}" ]]
do
read -p "How many would you like to add? " choice
# ((choice++)) If choice=999, script will not read anything.
# If 0 <= choice <= 9, script will not never stopped.
# So, you should uncomment ((choice++)) to stop script running when choice become
# more than 9.
done