Check if a variable exists in a list in Bash

Question

I am trying to write a script in bash that check the validity of a user input.
I want to match the input (say variable x) to a list of valid values.

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Answer 1

Matvey is right, but you should quote $x and consider any kind of "spaces" (e.g. new line) with

[[ $list =~ (^|[[:space:]])"$x"($|[[:space:]]) ]] && echo 'yes' || echo 'no' 

so, i.e.

# list_include_item "10 11 12" "2"
function list_include_item {
  local list="$1"
  local item="$2"
  if [[ $list =~ (^|[[:space:]])"$item"($|[[:space:]]) ]] ; then
    # yes, list include item
    result=0
  else
    result=1
  fi
  return $result
}

end then

`list_include_item "10 11 12" "12"`  && echo "yes" || echo "no"

or

if `list_include_item "10 11 12" "1"` ; then
  echo "yes"
else 
  echo "no"
fi

Note that you must use "" in case of variables:

`list_include_item "$my_list" "$my_item"`  && echo "yes" || echo "no"