add checks

install.sh

@@ -4,6 +4,17 @@
 archlinux_mirror="https://mirrors.kernel.org/archlinux/"
 preserve_home_directories=true
 
+stdin_symlink="$(readlink /dev/fd/0)"
+if [ "${stdin_symlink#pipe:}" != "${stdin_symlink}" ]; then
+	echo "This script must be run from a file. Exiting." >&2
+	exit 1
+fi
+
+if [ -n "${POSIXLY_CORRECT}" ] || [ -z "${BASH_VERSION}" ]; then
+	unset POSIXLY_CORRECT
+	exec bash "$0" "$@"
+fi
+
 set -eu
 set -o pipefail
 shopt -s nullglob
@@ -13,7 +24,6 @@ export LC_ALL=C
 export LANG=C
 unset LANGUAGE
 
-### VARIABLES
 declare -A dependencies
 dependencies[pacman]=x