cpu: Implement steal/guest/guest_nice counters

steal (since Linux 2.6.11)
       (8) Stolen time, which is the time spent in
       other operating systems when running in a virtu‐
       alized environment

guest (since Linux 2.6.24)
       (9) Time spent running a virtual CPU for guest
       operating systems under the control of the Linux
       kernel.

guest_nice (since Linux 2.6.33)
       (10) Time spent running a niced guest (virtual
       CPU for guest operating systems under the con‐
       trol of the Linux kernel).

plugins/cpu

@@ -1,7 +1,17 @@
 config_cpu() {
   extinfo=""
-  if grep -q '^cpu \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\}' /proc/stat; then
+  fields=$(grep '^cpu ' /proc/stat | wc -w)
-    extinfo="iowait irq softirq"
+  if [ "$fields" -gt 5 ]; then
+    extinfo="$extinfo iowait irq softirq"
+    if [ "$fields" -gt 8 ]; then
+      extinfo="$extinfo steal"
+      if [ "$fields" -gt 9 ]; then
+        extinfo="$extinfo guest"
+        if [ "$fields" -gt 10 ]; then
+          extinfo="$extinfo guest_nice"
+        fi
+      fi
+    fi
   fi
   # shellcheck disable=SC2126
   NCPU=$(grep '^cpu[0-9]\+ ' /proc/stat | wc -l)
@@ -45,7 +55,7 @@ config_cpu() {
   echo "idle.max 5000"
   echo "idle.type DERIVE"
   echo "idle.info Idle CPU time"
-  if [ -n "$extinfo" ]; then
+  if [ "$fields" -gt 5 ]; then
     echo "iowait.label iowait"
     echo "iowait.draw STACK"
     echo "iowait.min 0"
@@ -64,21 +74,51 @@ config_cpu() {
     echo "softirq.max 5000"
     echo "softirq.type DERIVE"
     echo "softirq.info CPU time spent handling 'batched' interrupts"
+    if [ "$fields" -gt 8 ]; then
+        echo "steal.label steal"
+        echo "steal.draw STACK"
+        echo "steal.min 0"
+        echo "steal.max 5000"
+        echo "steal.type DERIVE"
+        echo "steal.info The time that a virtual CPU had runnable tasks, but the virtual CPU itself was not running"
+        if [ "$fields" -gt 9 ]; then
+          echo "guest.label guest"
+          echo "guest.draw STACK"
+          echo "guest.min 0"
+          echo "guest.max 5000"
+          echo "guest.type DERIVE"
+          echo "guest.info The time spent running a virtual CPU for guest operating systems"
+          if [ "$fields" -gt 10 ]; then
+            echo "guest_nice.label guest_nice"
+            echo "guest_nice.draw STACK"
+            echo "guest_nice.min 0"
+            echo "guest_nice.max 5000"
+            echo "guest_nice.type DERIVE"
+            echo "guest_nice.info The time spent running a virtual CPU for a niced guest operating system"
+          fi
+        fi
+    fi
   fi
 }
 fetch_cpu() {
-  extinfo=""
+  fields=$(grep '^cpu ' /proc/stat | wc -w)
-  if grep -q '^cpu \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\} \{1,\}[0-9]\{1,\}' /proc/stat; then
-    extinfo="iowait irq softirq"
-  fi
   CINFO=$(grep '^cpu ' /proc/stat | cut -c6-)
   echo "user.value" "$(echo "$CINFO" | cut -d " " -f 1)"
   echo "nice.value" "$(echo "$CINFO" | cut -d " " -f 2)"
   echo "system.value" "$(echo "$CINFO" | cut -d " " -f 3)"
   echo "idle.value" "$(echo "$CINFO" | cut -d " " -f 4)"
-  if [ -n "$extinfo" ]; then
+  if [ "$fields" -gt 5 ]; then
     echo "iowait.value" "$(echo "$CINFO" | cut -d " " -f 5)"
     echo "irq.value" "$(echo "$CINFO" | cut -d " " -f 6)"
     echo "softirq.value" "$(echo "$CINFO" | cut -d " " -f 7)"
+    if [ "$fields" -gt 8 ]; then
+      echo "steal.value" "$(echo "$CINFO" | cut -d " " -f 8)"
+      if [ "$fields" -gt 9 ]; then
+        echo "guest.value" "$(echo "$CINFO" | cut -d " " -f 9)"
+        if [ "$fields" -gt 10 ]; then
+          echo "guest_nice.value" "$(echo "$CINFO" | cut -d " " -f 10)"
+        fi
+      fi
+    fi
   fi
 }