Read a config file in BASH without using “source”

Question

I\'m attempting to read a config file that is formatted as follows:

USER = username
TARGET = arrows

I realize that if I got rid of the spaces,

Answer 1

I have a script which only takes a very limited number of settings, and processes them one at a time, so I've adapted SiegeX's answer to whitelist the settings I care about and act on them as it comes to them.

I've also removed the requirement for spaces around the = in favour of ignoring any that exist using the trim function from another answer.

function trim()
{
    local var=$1;
    var="${var#"${var%%[![:space:]]*}"}";   # remove leading whitespace characters
    var="${var%"${var##*[![:space:]]}"}";   # remove trailing whitespace characters
    echo -n "$var";
}

while read line; do
    if [[ "$line" =~ ^[^#]*= ]]; then
        setting_name=$(trim "${line%%=*}");
        setting_value=$(trim "${line#*=}");

        case "$setting_name" in
            max_foos)
                prune_foos $setting_value;
            ;;
            max_bars)
                prune_bars $setting_value;
            ;;
            *)
                echo "Unrecognised setting: $setting_name";
            ;;
        esac;
    fi
done <"$config_file";