Make shopt change local to function

Question

I\'m trying to write a bash function that uses nocasematch without changing the callers setting of the option. The function definition is:

is_he         


        

Answer 1

You can use an associative array to remember the previous setting and then use it for reverting to the earlier setting, like this:

shopt_set

declare -gA _shopt_restore
shopt_set() {
    local opt count
    for opt; do
        if ! shopt -q "$opt"; then
            echo "$opt not set, setting it"
            shopt -s "$opt"
            _shopt_restore[$opt]=1
            ((count++))
        else
            echo "$opt set already"
        fi
    done
}

shopt_unset

shopt_unset() {
    local opt restore_type
    for opt; do
        restore_type=${_shopt_restore[$opt]}
        if shopt -q "$opt"; then
            echo "$opt set, unsetting it"
            shopt -u "$opt"
            _shopt_restore[$opt]=2
        else
            echo "$opt unset already"
        fi
        if [[ $restore_type == 1 ]]; then
            unset _shopt_restore[$opt]
        fi
    done
}

shopt_restore

shopt_restore() {
    local opt opts restore_type
    if (($# > 0)); then
        opts=("$@")
    else
        opts=("${!_shopt_restore[@]}")
    fi
    for opt in "${opts[@]}"; do
        restore_type=${_shopt_restore[$opt]}
        case $restore_type in
        1)
            echo "unsetting $opt"
            shopt -u "$opt"
            unset _shopt_restore[$opt]
            ;;
        2)
            echo "setting $opt"
            shopt -s "$opt"
            unset _shopt_restore[$opt]
            ;;
        *)
            echo "$opt wasn't changed earlier"
            ;;
        esac
    done
}

Then use these functions as:

... some logic ...
shopt_set nullglob globstar      # set one or more shopt options
... logic that depends on the above shopt settings
shopt_restore nullglob globstar  # we are done, revert back to earlier setting

or

... some logic ...
shopt_set nullglob
... some more logic ...
shopt_set globstar
... some more logic involving shopt_set and shopt_unset ...
shopt_restore             # restore everything

Complete source code here: https://github.com/codeforester/base/blob/master/lib/shopt.sh