diff --git a/plugins/virtualbox/virtualbox_cpu_kernel b/plugins/virtualbox/virtualbox_cpu_kernel
index 5f4db938..d39db3fd 100755
--- a/plugins/virtualbox/virtualbox_cpu_kernel
+++ b/plugins/virtualbox/virtualbox_cpu_kernel
@@ -37,8 +37,8 @@ if [ "$1" = "config" ]; then
         echo 'graph_info This graph shows the percentage of processor time spent in kernel mode by the every single VM process.'
         echo 'graph_category Virtualization'
         echo 'graph_period second'
-        vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read VM_NAME; do
-                VM_NAME_PRINT=`echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g'`
+        vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read -r VM_NAME; do
+                VM_NAME_PRINT=$(echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g')
                 echo "${VM_NAME_PRINT}_kernel.label ${VM_NAME}"
         done
         exit 0
@@ -47,8 +47,7 @@ fi
 vboxmanage metrics setup --period 5 --samples 3
 sleep 5
 
-vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read VM_NAME; do
-        VM_NAME_PRINT=`echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g'`
-        vboxmanage metrics query "${VM_NAME}" CPU/Load/Kernel | grep -E "^${VM_NAME}" | sed -r 's/^.*([0-9]+\.[0-9]+)%/'''${VM_NAME_PRINT}'''_kernel.value \1/'
+vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read -r VM_NAME; do
+VM_NAME_PRINT=$(echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g')
+        vboxmanage metrics query "${VM_NAME}" CPU/Load/Kernel | grep -E "^${VM_NAME}" | sed -r 's/^.*([0-9]+\.[0-9]+)%/'"${VM_NAME_PRINT}"'_kernel.value \1/'
 done
-
diff --git a/plugins/virtualbox/virtualbox_cpu_user b/plugins/virtualbox/virtualbox_cpu_user
index 8bd77674..33c1b469 100755
--- a/plugins/virtualbox/virtualbox_cpu_user
+++ b/plugins/virtualbox/virtualbox_cpu_user
@@ -37,8 +37,8 @@ if [ "$1" = "config" ]; then
         echo 'graph_info This graph shows the percentage of processor time spent in user mode by the every single VM process.'
         echo 'graph_category Virtualization'
         echo 'graph_period second'
-        vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read VM_NAME; do
-                VM_NAME_PRINT=`echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g'`
+        vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read -r VM_NAME; do
+                VM_NAME_PRINT=$(echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g')
                 echo "${VM_NAME_PRINT}_user.label ${VM_NAME}"
         done
         exit 0
@@ -47,8 +47,7 @@ fi
 vboxmanage metrics setup --period 5 --samples 3
 sleep 5
 
-vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read VM_NAME; do
-        VM_NAME_PRINT=`echo -e "${VM_NAME}" |  sed 's/[^A-Za-z0-9_]/_/g'`
-        vboxmanage metrics query "${VM_NAME}" CPU/Load/User | grep -E "^${VM_NAME}" | sed -r 's/^.*([0-9]+\.[0-9]+)%/'''${VM_NAME_PRINT}'''_user.value \1/'
+vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read -r VM_NAME; do
+        VM_NAME_PRINT=$(echo -e "${VM_NAME}" |  sed 's/[^A-Za-z0-9_]/_/g')
+        vboxmanage metrics query "${VM_NAME}" CPU/Load/User | grep -E "^${VM_NAME}" | sed -r 's/^.*([0-9]+\.[0-9]+)%/'"${VM_NAME_PRINT}"'_user.value \1/'
 done
-
diff --git a/plugins/virtualbox/virtualbox_ram_usage b/plugins/virtualbox/virtualbox_ram_usage
index e81db92c..6205c638 100755
--- a/plugins/virtualbox/virtualbox_ram_usage
+++ b/plugins/virtualbox/virtualbox_ram_usage
@@ -34,7 +34,7 @@ if [ "$1" = "autoconf" ]; then
 fi
 
 if [ "$1" = "config" ]; then
-RAMTOT=`free -b | grep Mem | awk '{print $2}'`
+        RAMTOT=$(free -b | grep Mem | awk '{print $2}')
         echo 'graph_title Memory usage of virtual machines'
         echo "graph_args --base 1024 -r --lower-limit 0 --upper-limit $RAMTOT --units-exponent 9"
         echo 'graph_vlabel GB'
@@ -42,11 +42,11 @@ RAMTOT=`free -b | grep Mem | awk '{print $2}'`
         echo 'graph_category Virtualization'
         echo 'graph_period second'
         I=0
-        vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read VM_NAME; do
-                VM_NAME_PRINT=`echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g'`
+        vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read -r VM_NAME; do
+                VM_NAME_PRINT=$(echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g')
                 echo "${VM_NAME_PRINT}.label ${VM_NAME}"
-  	echo "${VM_NAME_PRINT}.cdef ${VM_NAME_PRINT},1024,*"
-                if [ ${I} -eq 0 ]; then
+                echo "${VM_NAME_PRINT}.cdef ${VM_NAME_PRINT},1024,*"
+                if [ "$I" -eq 0 ]; then
                         echo "${VM_NAME_PRINT}.draw AREA"
                 else
                         echo "${VM_NAME_PRINT}.draw STACK"
@@ -59,8 +59,8 @@ fi
 vboxmanage metrics setup --period 5 --samples 3
 sleep 5
 
-vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read VM_NAME; do
-        VM_NAME_PRINT=`echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g'` # s/[.]/_/g;s/[ ]/_/g;s/[-]/_/g
-        vboxmanage metrics query "${VM_NAME}" RAM/Usage/Used | grep -E "^${VM_NAME}" | sed -r 's/^.* ([0-9]+) kB$/'''${VM_NAME_PRINT}'''.value \1/'
+vboxmanage list vms | sed -r 's/^\"(.*)\" \{.*\}$/\1/' | while read -r VM_NAME; do
+        VM_NAME_PRINT=$(echo -e "${VM_NAME}" | sed 's/[^A-Za-z0-9_]/_/g') # s/[.]/_/g;s/[ ]/_/g;s/[-]/_/g
+        vboxmanage metrics query "${VM_NAME}" RAM/Usage/Used | grep -E "^${VM_NAME}" | sed -r 's/^.* ([0-9]+) kB$/'"${VM_NAME_PRINT}"'.value \1/'
 done