CODEWITHSUNDEEP
bash
Village
Village

Reputation: 24363

How to check if a variable contains a character not found in a list within a BASH conditional?

I need to create a BASH conditional that checks if any unusual characters are found. If any character is not one of these, the conditional returns true: c, d, f, g, h, T, ,, ?, !. E.g.:

if [[ "$variable" contains something that is not [cdfghZ,?!] ]]
then
    echo "The variable contains an unknown character."
fi

How can I check for characters not found in a list with a BASH conditional?

Upvotes: 2

Views: 125

Answers (4)

tripleee
tripleee

Reputation: 189357

Good old case has this built in, and is portable to all Bourne shells.

case $variable in *[!cdfghZ,?!]* ) 
    echo "The variable contains an unknown character." >&2 ;;
esac

Upvotes: 4

chepner
chepner

Reputation: 531045

You can use extended patterns (which are used by default inside [[...]] in bash 4.2 but need to be explicitly enabled in earlier versions):

shopt -s extglob  # if necessary
if [[ $variable != +([cdfghZ,?!]) ]]; then

The pattern +(...) matches a string containing one or more characters, each of which must match the pattern inside the parentheses. It is essentially equivalent to the regular expression [cdfghZ,?!]+.

Upvotes: 2

anubhava
anubhava

Reputation: 785058

You can use globbing:

[[ "$variable" == *[^cdfghT,?\!]* ]]

PS: ! needs to be used as \! to escape history event expansion.

Upvotes: 4

choroba
choroba

Reputation: 241828

You can check with a regular expression:

 if [[ $variable =~ [^cdfghT,?\!] ]] ; then
 ...

Upvotes: 3

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