ping plugin: use -W for linux, -t for bsd/darwin

closes #443

plugins/inputs/ping/ping.go

@@ -5,6 +5,7 @@ package ping
 import (
 	"errors"
 	"os/exec"
+	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -133,7 +134,15 @@ func (p *Ping) args(url string) []string {
 		args = append(args, "-i", strconv.FormatFloat(p.PingInterval, 'f', 1, 64))
 	}
 	if p.Timeout > 0 {
-		args = append(args, "-t", strconv.FormatFloat(p.Timeout, 'f', 1, 64))
+		switch runtime.GOOS {
+		case "darwin", "freebsd":
+			args = append(args, "-t", strconv.FormatFloat(p.Timeout, 'f', 1, 64))
+		case "linux":
+			args = append(args, "-W", strconv.FormatFloat(p.Timeout, 'f', 1, 64))
+		default:
+			// Not sure the best option here, just assume GNU ping?
+			args = append(args, "-W", strconv.FormatFloat(p.Timeout, 'f', 1, 64))
+		}
 	}
 	if p.Interface != "" {
 		args = append(args, "-I", p.Interface)