.profile: Small improvements

I think
Not really, actually

.profile

@@ -39,6 +39,9 @@
 # shellcheck disable=1117
 
 # Environment variables
+# First, what shell are we?
+_baseshell="$(basename "$0")"
+
 # Use Vim if we have it
 export EDITOR="vi"
 command -v vim > /dev/null 2>&1 && export EDITOR="vim"
@@ -65,7 +68,7 @@ PATH="$desiredpath:$PATH"
 
 # Grab pip completion, if it exists
 if command -v pip > /dev/null 2>&1; then
-	case "$(basename "$SHELL")" in
+	case "$_baseshell" in
 		*bash)
 			if ! [ -f "$HOME/.pip-completion-bash" ]; then
 				pip completion --bash > "$HOME/.pip-completion-bash"
@@ -171,10 +174,10 @@ _ps1() {
 		*bash)
 			prefix="${prefix}${fg_yellow}"
 			;;
-		ksh)
+		/bin/ksh)
 			prefix="${prefix}${fg_green}"
 			;;
-		sh)
+		/bin/sh)
 			prefix="${prefix}${fg_grey}"
 			;;
 		*)
@@ -191,15 +194,24 @@ _ps1() {
 	if ! [ "$exitcode" = "0" ]; then
 		fail="${fg_bold}${fg_red}?"
 	fi
-	# printf is used here less for its C-like arguments and more becasue
-	# POSIX echo doesn't have an option to not print a newline.
-	# Hence this warning is disabled
 	# shellcheck disable=2059
 	printf "[${prefix}${cpwd}${r}]${fail}${r}${fg_green}\$${r} "
 }
 
-if ! [ "$ZSH_NAME" ]; then
-	# I've got a different ZSH theme
+# And export our PS1
+case "$_baseshell" in
+	zsh)
+		# Don't do this on ZSH
+		# I have a custom theme for that
+		;;
+	sh)
+		export PS1=''
+		;;
+	*)
 		export PS1='$(_ps1)'
-fi
+		;;
+esac
+
+# Clean up
+unset _baseshell