Bash: Syntax Error on @()

Question

I have the following function in my .bashrc file:

extract() {
    local c e i

    (($#)) || return

    for i; do
        c=''
        e=1

        if [[ ! -r $i ]]; then
            echo "$0: file is unreadable: \`$i'" >&2
            continue
        fi

        case $i in
        *.t@(gz|lz|xz|b@(2|z?(2))|a@(z|r?(.@(Z|bz?(2)|gz|lzma|xz)))))
               c='bsdtar xvf';;
        *.7z)  c='7z x';;
        *.Z)   c='uncompress';;
        *.bz2) c='bunzip2';;
        *.exe) c='cabextract';;
        *.gz)  c='gunzip';;
        *.rar) c='unrar x';;
        *.xz)  c='unxz';;
        *.zip) c='unzip';;
        *)     echo "$0: unrecognized file extension: \`$i'" >&2
               continue;;
        esac

        command $c "$i"
        e=$?
    done

    return $e
}

now this has been working perfectly for me on my current Arch Linux system. Recently, I installed the new, void-linux distro and tried to use my old .bashrc on it.

However, on Void-Linux, this functions throws an error:

syntax error near unexpected token '('

and points to this line:

*.t@(gz|lz|xz|b@(2|z?(2))|a@(z|r?(.@(Z|bz?(2)|gz|lzma|xz)))))

Some investigation returned that the Bash on that distro refuses to read the @() pattern and hence returns an error. I remember using the same function on a Debian Stable system a couple of months ago too.

Can anyone point out why this code doesn't seem to be portable? And where the error is?

Answer 1

As mentioned in my comment, that is a common error people see when trying to use extended globs(shopt -s extglob) before enabling the option. This includes function definitions.