mjhjmtu

Is it possible to check if a variable is contained inside an array using case? I would like to do something like

ARR=( opt1 opt2 opt3 );

case $1 in
 $ARR)
 echo "Option is contained in the array";
 *)
 echo "Option is not contained in the array";
esac

With ksh93, thanks to this bug, you can do:

IFS='|'
ARR=( opt1 opt2 opt3 )

IFS='|'
case $1 in
 (@("$ARR[*]"))
 echo "Option is contained in the array";;
 (*)
 echo "Option is not contained in the array";;
esac

(I wouldn't rely on it as the bug might get fixed in the future).

With zsh, you could do:

case $ARR[(Ie)$1]
 (0)
 echo "Option is not contained in the array";;
 (*)
 echo "Option is contained in the array";;
esac

(though, you'd probably rather want to use if ((ARR[(Ie)$1])); then echo is present... here rather than a case construct).

$array[(I)pattern] returns the index of the last element that matches the pattern in the array, or 0 otherwise. The e flag is for exact match (as opposed to pattern match).

With bash, ksh, yash, zsh, if you're ready to assume that $ARR and $1 don't contain a certain character like @, and that $ARR won't be empty, you can do:

IFS=@
case "@$ARR[*]@" in
 (*"@$1@"*)
 echo "Option is contained in the array";;
 (*)
 echo "Option is not contained in the array";;
esac

With bash -O extglob, zsh -o kshglob -o globsubst, you could define a helper that builds a pattern based on the elements of the array:

arraypat() 
 awk '
 BEGIN
 if (ARGC <= 1) print "!(*)"
 else 
 for (i = 1; i < ARGC; i++) 
 gsub(/[
 print "@(" s ")"
 
 ' "$@"


case $1 in
 ($(arraypat "$ARR[@]"))
 echo "Option is contained in the array";;
 (*)
 echo "Option is not contained in the array";;
esac

Not really in a compact and easy to use way. Remember that $ARR will expand to only the first element of the array, opt1 in your example.

You could use "$ARR[@]", but using your data this would give a false positive for the string 1 opt.

With more recent versions of bash, you could consider using an associative array:

declare -A arr
arr=( [opt1]=1 [opt2]=1 [opt3]=1 )

if [[ "$arr[$1]" -eq 1 ]]; then
 # $1 is a key in arr
else
 # is not
fi

Why would you want to do it with case? It's meant for string pattern matching, not per-element matching.

Frankly, if you need the "contains" test often and want to make it short because of that, just put the hard part in a function instead of using ugly workarounds:

#!/bin/bash
ARR=( foo bar doo );

contains() 
 typeset _x;
 typeset -n _A="$1"
 for _x in "$_A[@]" ; do
 [ "$_x" = "$2" ] && return 0
 done
 return 1


if contains ARR "$1" ; then
 echo ""$1" is contained in ARR"
else
 echo ""$1" not contained in ARR"
fi

(That should also work in ksh)