FIX: remove `os.stat` in order to fit in windows

Signed-off-by: 赵栩彬 <zhaoxubin2016@mail.com>

main.go

@@ -94,17 +94,34 @@ func main() {
 	level.Info(logger).Log("msg", "Starting systemd_exporter", "version", version.Info())
 	level.Info(logger).Log("msg", "Build context", "build_context", version.BuildContext())
 
-	devices := *smartctlDevices
-
-	if len(devices) == 0 {
-		level.Info(logger).Log("msg", "No devices specified, trying to load them automatically")
+	// Scan the host devices
 	json := readSMARTctlDevices(logger)
-		scannedDevices := json.Get("devices").Array()
-		for _, d := range scannedDevices {
-			device := d.Get("name").String()
-			level.Info(logger).Log("msg", "Found device", "device", device)
-			devices = append(devices, device)
+	scanDevices := json.Get("devices").Array()
+	scanDevicesSet := make(map[string]bool)
+	var scanDeviceNames []string
+	for _, d := range scanDevices {
+		deviceName := d.Get("name").String()
+		level.Debug(logger).Log("msg", "Found device", "name", deviceName)
+		scanDevicesSet[deviceName] = true
+		scanDeviceNames = append(scanDeviceNames, deviceName)
 	}
+
+	// Read the configuration and verify that it is available
+	devices := *smartctlDevices
+	var readDeviceNames []string
+	for _, device := range devices {
+		if _, ok := scanDevicesSet[device]; ok {
+			readDeviceNames = append(readDeviceNames, device)
+		} else {
+			level.Warn(logger).Log("msg", "Device unavailable", "name", device)
+		}
+	}
+
+	if len(readDeviceNames) > 0 {
+		devices = readDeviceNames
+	} else {
+		level.Info(logger).Log("msg", "No devices specified, trying to load them automatically")
+		devices = scanDeviceNames
 	}
 
 	if len(devices) == 0 {

readjson.go

@@ -16,7 +16,6 @@ package main
 import (
 	"fmt"
 	"io/ioutil"
-	"os"
 	"os/exec"
 	"strings"
 	"time"
@@ -94,7 +93,6 @@ func readData(logger log.Logger, device string) (gjson.Result, error) {
 		return readFakeSMARTctl(logger, device), nil
 	}
 
-	if _, err := os.Stat(device); err == nil {
 	cacheValue, cacheOk := jsonCache[device]
 	if !cacheOk || time.Now().After(cacheValue.LastCollect.Add(*smartctlInterval)) {
 		json, ok := readSMARTctl(logger, device)
@@ -106,8 +104,6 @@ func readData(logger log.Logger, device string) (gjson.Result, error) {
 	}
 	return cacheValue.JSON, nil
 }
-	return gjson.Parse("{}"), fmt.Errorf("Device %s unavialable", device)
-}
 
 // Parse smartctl return code
 func resultCodeIsOk(logger log.Logger, SMARTCtlResult int64) bool {