smartmon.sh: locate smartctl tool on non-Linux systems (#240)

Allow execution of `smartctl` even if it is installed in an unexpected
(for Linux) path.

Some OS, (e.g.: FreeBSD) do not install `smartctl` under the `usr/sbin/`
path, but instead use another path like `/usr/local/sbin/`.
This commit makes use of the `which` command to locate the `smartctl` in
the `PATH` and execute from there. As such it does not make any
assumption where `smartctl` is installed, improving portability.

---------

Signed-off-by: cristian-caloghera <[email protected]>

Author: cristian-caloghera

smartmon.sh

@@ -167,7 +167,7 @@ format_output() {
     awk -F'{' "${output_format_awk}"
 }
 
-smartctl_version="$(/usr/sbin/smartctl -V | awk 'NR==1 && $1 == "smartctl" {print $2}')"
+smartctl_version="$(smartctl -V | awk 'NR==1 && $1 == "smartctl" {print $2}')"
 
 echo "smartctl_version{version=\"${smartctl_version}\"} 1" | format_output
 
@@ -176,28 +176,28 @@ if [[ ${smartctl_version%.*} -lt 6 ]]; then
   exit 0
 fi
 
-device_list="$(/usr/sbin/smartctl --scan-open | awk '/^\/dev/{print $1 "|" $3}')"
+device_list="$(smartctl --scan-open | awk '/^\/dev/{print $1 "|" $3}')"
 
 for device in ${device_list}; do
   disk="$(echo "${device}" | cut -f1 -d'|')"
   type="$(echo "${device}" | cut -f2 -d'|')"
   active=1
   echo "smartctl_run{disk=\"${disk}\",type=\"${type}\"}" "$(TZ=UTC date '+%s')"
   # Check if the device is in a low-power mode
-  /usr/sbin/smartctl -n standby -d "${type}" "${disk}" > /dev/null || active=0
+  smartctl -n standby -d "${type}" "${disk}" > /dev/null || active=0
   echo "device_active{disk=\"${disk}\",type=\"${type}\"}" "${active}"
   # Skip further metrics to prevent the disk from spinning up
   test ${active} -eq 0 && continue
   # Get the SMART information and health
-  /usr/sbin/smartctl -i -H -d "${type}" "${disk}" | parse_smartctl_info "${disk}" "${type}"
+  smartctl -i -H -d "${type}" "${disk}" | parse_smartctl_info "${disk}" "${type}"
   # Get the SMART attributes
   case ${type} in
-  sat) /usr/sbin/smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
-  sat+megaraid*) /usr/sbin/smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
-  scsi) /usr/sbin/smartctl -A -d "${type}" "${disk}" | parse_smartctl_scsi_attributes "${disk}" "${type}" ;;
-  megaraid*) /usr/sbin/smartctl -A -d "${type}" "${disk}" | parse_smartctl_scsi_attributes "${disk}" "${type}" ;;
-  nvme*) /usr/sbin/smartctl -A -d "${type}" "${disk}" | parse_smartctl_scsi_attributes "${disk}" "${type}" ;;
-  usbprolific) /usr/sbin/smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
+  sat) smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
+  sat+megaraid*) smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
+  scsi) smartctl -A -d "${type}" "${disk}" | parse_smartctl_scsi_attributes "${disk}" "${type}" ;;
+  megaraid*) smartctl -A -d "${type}" "${disk}" | parse_smartctl_scsi_attributes "${disk}" "${type}" ;;
+  nvme*) smartctl -A -d "${type}" "${disk}" | parse_smartctl_scsi_attributes "${disk}" "${type}" ;;
+  usbprolific) smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
   *)
       (>&2 echo "disk type is not sat, scsi, nvme or megaraid but ${type}")
     exit