1 files changed, 7 insertions, 1 deletions
diff --git a/power_now b/power_now
index 1fb31aa..718e98d 100755
--- a/power_now
+++ b/power_now
@@ -12,10 +12,16 @@ while getopts "b:mqt" o; do case "${o}" in
   b) BATTERY="$OPTARG" ;;
 esac done
 
+error () {
+  printf "%s\n" "$@"
+  exit 1
+}
+
 #TOTALPOWER='0'
 
 case "$BATTERY" in
   "ALL")
+    ls -1 /sys/class/power_supply | grep -q 'BAT' || error "Are there no batteries?"
     for battery in $(ls -1 /sys/class/power_supply | grep 'BAT'); do
       DIRNAME="/sys/class/power_supply/${battery}"
       if [ -f "${DIRNAME}/power_now" ]; then
@@ -59,7 +65,7 @@ case "$BATTERY" in
     ;;
   *)
     DIRNAME="/sys/class/power_supply/${BATTERY}"
-    [ -d "${DIRNAME}" ] || echo "No such battery!"
+    [ -d "${DIRNAME}" ] || error "No such battery!"
     if [ -f "${DIRNAME}/power_now" ]; then
       if [ -n "${MILLIWATTS}" ]; then
         POWER="$(cat "${DIRNAME}/power_now" | awk '{print $1/1e3}' | head -1)"