@@ -1,6 +1,7 @@

 #!/usr/bin/env bash

+set -e -u -o pipefail

-DUAL_CONTROL="$(which dual_control)"

+DUAL_CONTROL="$(command -v dual_control || printf '')"

 DUAL_CONTROL="${DUAL_CONTROL:-./dual_control}"

 get_key() {

@@ -14,7 +15,7 @@ get_token() {

 qr() {

   local VAL=$1

   local MODE=${2:-ANSI}

-  shift 2

+  shift 2 || true

   qrencode -t $MODE $VAL

 }

@@ -30,7 +31,7 @@ main() {

   local KEY_URL="$(get_url "$KEY")"

   local NONINTERACTIVE="$1"

-  if which qrencode > /dev/null; then

+  if command -v qrencode > /dev/null; then

     qr $KEY_URL

   else

     echo "Run 'yum install qrencode' to get a QR code"

@@ -51,8 +52,8 @@ main() {

   popd > /dev/null

 }

-case "$1" in

-  '-h')

+case "${1:-}" in

+'-h')

   cat <<EOF

 USAGE:

   $(basename $0) [--help]

@@ -60,6 +61,7 @@ USAGE:

 EOF

   exit 0

   ;;

+

 *)

-  main "$1"

+  main "${1:-}"

 esac