diff --git a/kvmstats/kvmstats b/kvmstats/kvmstats
index 25ae4ec..cf2416b 100644
--- a/kvmstats/kvmstats
+++ b/kvmstats/kvmstats
@@ -1,40 +1,32 @@
 #!/bin/sh
 
-set -e
-
 error () {
     echo "$0": "$@" >&2
     exit 1
 }
 
 usage () {
-    echo 'usage: kvmstats [-a] [-u k|m|g] [-o human|html|csv]' >&2
+    echo 'usage:' "$0" '[-a] [-u k|m|g] [-o human|html|csv]' >&2
     exit 1
 }
 
 for DEP in bc virsh
 do
-    command -v $DEP > /dev/null || error $DEP command not found
+    command -v "$DEP" > /dev/null || error "$DEP" 'command not found'
 done
 
-POW=$(echo 1024 ^ 3 | bc)
-FMT=human
-while [ $# -ne 0 ]
+POW="$(echo '1024 ^ 3' | bc)"
+FMT='human'
+while [ "$#" -ne 0 ]
 do
-    case $1 in
+    case "$1" in
     '-a')
-        SHOW_AVAIL=y
+        SHOW_AVAIL='y'
         ;;
     '-o')
-        case $2 in
-        'human')
-            FMT=human
-            ;;
-        'html')
-            FMT=html
-            ;;
-        'csv')
-            FMT=csv
+        case "$2" in
+        'csv'|'html'|'human')
+            FMT="$2"
             ;;
         *)
             usage
@@ -43,15 +35,15 @@ do
         shift
         ;;
     '-u')
-        case $2 in
+        case "$2" in
         'k')
-            POW=$(echo 1024 ^ 1 | bc)
+            POW="$(echo '1024 ^ 1' | bc)"
             ;;
         'm')
-            POW=$(echo 1024 ^ 2 | bc)
+            POW="$(echo '1024 ^ 2' | bc)"
             ;;
         'g')
-            POW=$(echo 1024 ^ 3 | bc)
+            POW="$(echo '1024 ^ 3' | bc)"
             ;;
         *)
             usage
@@ -73,13 +65,13 @@ do
 
     # mem
     # libvirt stores memory in KiB, POW must be lowered by 1
-    virsh dommemstat "$VM" 2>&- | awk 'BEGIN{ret=1}$1~/^actual$/{print $2 / '$((POW / 1024))';ret=0}END{exit ret}' ||
+    virsh dommemstat "$VM" 2> /dev/null | awk 'BEGIN{ret=1}$1~/^actual$/{print $2 / '$((POW / 1024))';ret=0}END{exit ret}' ||
         virsh dumpxml "$VM" | awk -F'[<>]' '$2~/^memory unit/{print $3/'$((POW / 1024))'}'
 
     # disk
     for BLK in $(virsh domblklist "$VM" | sed '1,2d;/-$/d;/^$/d' | awk '{print $1}')
     do
-        virsh domblkinfo "$VM" "$BLK" 2>&-
+        virsh domblkinfo "$VM" "$BLK" 2> /dev/null
     done | awk '/Physical:/ { size += $2 } END { print int(size / '${POW}') }'
 
     # state
@@ -91,7 +83,7 @@ done | xargs -n5 | {
         nproc
         awk '/^MemTotal:/ { print int($2 / '$((POW / 1024))' ) }' /proc/meminfo
     } | xargs -r printf 'AVAILABLE %s %s %s %s\n'
-} | case $FMT in
+} | case "$FMT" in
 'human')
     column -t
     ;;