Check if a variable exists in a list in Bash

how about

echo $list | grep -w -q $x

you could either check the output or $? of above line to make the decision.

grep -w checks on whole word patterns. Adding -q prevents echoing the list.

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

or create a function:

contains() {
    [[ $1 =~ (^|[[:space:]])$2($|[[:space:]]) ]] && exit(0) || exit(1)
}

to use it:

contains aList anItem
echo $? # 0： match, 1: failed

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