Bash subcommands with arguments

For sub-command you can handle it this way:

function main(){
    if (( ${#} == 0 )); then
        main_help 0;
    fi

    case ${1} in
        help | version | encrypt | decrypt )
            $1 "${@:2}";
        ;;
        * )
            echo "unknown command: $1";
            main_help 1;
            exit 1;
        ;;
    esac
}

main "$@";

Then wrap each sub-command is a function. And inside each function you will have isolated options and parsing it separately.

For example:

function decrypt(){
    if [[ ${#} == 0 ]]; then
        decrypt_help;
    fi

    local __filename='';
    local __salt='';
    local __anchor=false;
    local error_message='';

    while [ ${#} -gt 0 ]; do
        error_message="Error: a value is needed for '$1'";
        case $1 in
            -f | --file )
                __filename=${2:?$error_message}
                shift 2;
            ;;
            -s | --salt )
                __salt=${2:?$error_message}
                shift 2;
            ;;
            -a | --anchor )
                __anchor=${2:?$error_message}
                shift 2;
            ;;
            * )
                echo "unknown option $1";
                break;
            ;;
        esac
    done

    echo filename: ${__filename:-empty};
    echo salt: ${__salt:-empty};
    echo anchor: $__anchor;

    exit 0;
}

Here is a full version bash-CLI-template I have used in may projects

demo ;)