Add command logging to snmp input at debug level (#5474)

plugins/inputs/snmp/snmp.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
+	"log"
 	"math"
 	"net"
 	"os/exec"
@@ -15,7 +16,7 @@ import (
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/plugins/inputs"
-
+	"github.com/influxdata/wlog"
 	"github.com/soniah/gosnmp"
 )
 
@@ -84,6 +85,14 @@ var execCommand = exec.Command
 // execCmd executes the specified command, returning the STDOUT content.
 // If command exits with error status, the output is captured into the returned error.
 func execCmd(arg0 string, args ...string) ([]byte, error) {
+	if wlog.LogLevel() == wlog.DEBUG {
+		quoted := make([]string, 0, len(args))
+		for _, arg := range args {
+			quoted = append(quoted, fmt.Sprintf("%q", arg))
+		}
+		log.Printf("D! [inputs.snmp] Executing %q %s", arg0, strings.Join(quoted, " "))
+	}
+
 	out, err := execCommand(arg0, args...).Output()
 	if err != nil {
 		if err, ok := err.(*exec.ExitError); ok {