diff --git a/kvmstats b/kvmstats
index 6d91bff..b1d74c2 100755
--- a/kvmstats
+++ b/kvmstats
@@ -1,9 +1,9 @@
 #!/bin/sh
 
-set -e -u
+set -e
 
 usage () {
-    echo 'usage: kvmstats.sh [-a] [-u K|M|G]'
+    echo 'usage: kvmstats [-a] [-u k|m|g]' >&2
     exit 1
 }
 
@@ -11,25 +11,24 @@ for DEP in bc virsh
 do
     if [ -z "$(which $DEP)" ]
     then
-        echo "kvmstats.sh: $DEP not found in \$PATH" 1>&2
+        echo "kvmstats: $DEP not found in \$PATH" >&2
         exit 1
     fi
 done
 
-SHOW_AVAIL=''
 POW=$(echo 1024 ^ 3 | bc)
 while [ $# -ne 0 ] && echo "$1" | grep -q '^-[[:alnum:]]'
 do
     case $1 in
     '-u')
         case $2 in
-        'K')
+        'k')
             POW=$(echo 1024 ^ 1 | bc)
             ;;
-        'M')
+        'm')
             POW=$(echo 1024 ^ 2 | bc)
             ;;
-        'G')
+        'g')
             POW=$(echo 1024 ^ 3 | bc)
             ;;
         *)
@@ -45,17 +44,15 @@ do
     shift
 done
 
-# since libvirt seems to store memoy in KiB, POW must be lowered by 1
-POW=$((POW / 1024))
-
 for VM in $(virsh list --name --all)
 do
     CPU=$(virsh vcpucount --maximum --current "$VM")
-    RAM=$(virsh domstats --balloon "$VM" | awk 'BEGIN { FS="=" } /balloon.maximum/ { print $2 / 1024 ^ 2 }')
+    # libvirt store memoy in KiB, POW must be lowered by 1
+    RAM=$(virsh domstats --balloon "$VM" | awk 'BEGIN { FS="=" } /balloon.maximum/ { print $2 / '$((POW / 1024))'}')
     DSK=$(for BLK in $(virsh domblklist "$VM" | sed '1,2d;/-$/d;/^$/d' | cut -d\  -f1)
           do
               virsh domblkinfo "$VM" "$BLK"
-          done | awk '/Physical:/ { size += $2 } END { print int(size / 1024 ^ 3) }')
+          done | awk '/Physical:/ { size += $2 } END { print int(size / '${POW}') }')
     RUN=$(virsh domstate "$VM" | grep -q '^running$' && echo yes || echo no)
     echo "$VM" "$CPU" "$RAM" "$DSK" "$RUN"
 done | (
@@ -64,7 +61,7 @@ done | (
     if [ "$SHOW_AVAIL" ]
     then
         AV_CPU=$(awk '/^processor/ { cpu++ } END { print cpu }' /proc/cpuinfo)
-        AV_MEM=$(awk '/^MemTotal:/ { print int($2 / 1024 ^ 2) }' /proc/meminfo)
+        AV_MEM=$(awk '/^MemTotal:/ { print int($2 / '$((POW / 1024))' ) }' /proc/meminfo)
         echo AVAILABLE "$AV_CPU" "$AV_MEM"
     fi
 ) | column -t