nvidiactl: Fix test condition, replace existing device nodes and fix shellcheck warning

nvidiactl/nvidiactl

@@ -16,6 +16,12 @@ use_nouveau () {
   exit 1
 }
 
+# Replace an existing node, for example from an earlier run of the service.
+make_chardev () {
+  rm -f "$1"
+  mknod -m 666 "$1" c "$2" "$3"
+}
+
 if [ -d /sys/module/nouveau ] ; then
   echo >&2 "NOTE: nouveau driver loaded already, using 'mxgfx-generic'."
   set_generic_mxgfx_link
@@ -26,17 +32,17 @@ PCIIDHINT_DIR=/usr/share/nvidia/pciidhints
 
 kver=$(uname -r)
 
-nvidiacards=( $(lspci -n | grep " 030[0,2]: 10de:" | cut -d ' ' -f 3) )
+mapfile -t nvidiacards < <(lspci -n | grep " 030[0,2]: 10de:" | cut -d ' ' -f 3)
 
-nvver=${nvidiacards[0]}
+pciid=${nvidiacards[0]}
 
-if [ -z ${nvver} ] ; then
+if [ -z "${pciid}" ] ; then
   echo >&2 "WARNING: no nvidia card found.."
   set_generic_mxgfx_link
   exit 0
 fi
 
-pciids="${PCIIDHINT_DIR}/${kver}-${nvver} ${PCIIDHINT_DIR}/${nvver}"
+pciids="${PCIIDHINT_DIR}/${kver}-${pciid} ${PCIIDHINT_DIR}/${pciid}"
 
 for leglvlhint in ${pciids} ; do
   if [ -h "${leglvlhint}" ] ; then
@@ -82,19 +88,19 @@ NVDEVS=$(lspci | grep -i NVIDIA)
 N3D=$(echo "$NVDEVS" | grep "3D controller" | wc -l)
 NVGA=$(echo "$NVDEVS" | grep "VGA compatible controller" | wc -l)
 N=$(( $N3D + $NVGA ))
-if [ ! -z $N ]; then
+if [ $N -gt 0 ]; then
   N=$(( $N - 1 ))
   for i in $(seq 0 $N); do
-   mknod -m 666 /dev/nvidia$i c 195 $i
+   make_chardev /dev/nvidia$i 195 $i
   done
-  mknod -m 666 /dev/nvidiactl c 195 255
+  make_chardev /dev/nvidiactl 195 255
 
   # CUDA
   if [ -e ${nvlink}/nvidia-uvm.ko ]; then
     insmod ${nvlink}/nvidia-uvm.ko
     D=$(grep nvidia-uvm /proc/devices | awk '{print $1}')
     if [ ! -z $D ]; then
-      mknod -m 666 /dev/nvidia-uvm c $D 0
+      make_chardev /dev/nvidia-uvm $D 0
     fi
   fi
   test -e  ${nvlink}/nvidia-modeset.ko && insmod ${nvlink}/nvidia-modeset.ko