Improve error reporting

This commit introduces several improvements to the way bosun reacts to
and reports errors.

Instead of doing nothing and exiting silently, alert the user and print
a short usage synopsis if bosun does not understand a command it was
passed. Also, alert the user and print available list types if the
`list` command was invoked with a type it does not understand.  Lastly,
check for the existence of a role before trying to `add`, `remove`, or
`rebuild` it.

1 files changed, 31 insertions, 4 deletions

diff --git a/bosun b/bosun
index c195176..cbc9718 100755
--- a/bosun
+++ b/bosun
@@ -2,20 +2,44 @@
 
 export STOW_DIR=/etc/portage/stow
 
+err() {
+	printf "bosun: %s\n" "$@" >&2
+}
+
+errx() {
+	err "$@"
+	exit 1
+}
+
+usage() {
+	printf "usage: bosun add role ...\n" >&2
+	printf "       bosun flush\n" >&2
+	printf "       bosun [list [type ...]]\n" >&2
+	printf "       bosun rebuild [role ...]\n" >&2
+	printf "       bosun remove [role ...]\n" >&2
+	exit 1
+}
+
+need_role() {
+	test $# -gt 0 || errx "this command requires at least one role"
+	for dir in "$@"; do
+		test -d "$STOW_DIR/$dir" || errx "no such role '$dir' in $STOW_DIR"
+	done
+}
+
 need_root() {
-	if test "$(id -u)" -ne 0; then
-		printf 'This action requires superuser access.\n'
-		exit 1
-	fi
+	test "$(id -u)" -eq 0 || errx "this action requires superuser access"
 }
 
 add() {
 	need_root
+	need_role "$@"
 	stow -S "$@"
 }
 
 remove() {
 	need_root
+	need_role "$@"
 	stow -D "$@"
 }
 
@@ -27,6 +51,7 @@ flush() {
 rebuild() {
 	need_root
 	if test $# -gt 0; then
+		need_role "$@"
 		stow -R "$@"
 	else
 		list | xargs -- stow -R
@@ -39,6 +64,7 @@ list() {
 		active) list_active;;
 		all) list_all;;
 		available) list_available;;
+		*) errx "no such list type '$subcmd'. Try: active, all, available"
 	esac
 }
 
@@ -71,4 +97,5 @@ case $cmd in
 	list) list "$@";;
 	rebuild) rebuild "$@";;
 	remove) remove "$@";;
+	*) err "no such command '$cmd'"; usage;;
 esac