Fix exec plugin panic with single binary

fixes #1330

CHANGELOG.md

+## v1.0 beta 2 [unreleased]
+
+### Features
+
+### Bugfixes
+
+- [#1330](https://github.com/influxdata/telegraf/issues/1330): Fix exec plugin panic when using single binary
+- [#1336](https://github.com/influxdata/telegraf/issues/1336): Fixed incorrect prometheus metrics source selection
+
 ## v1.0 beta 1 [2016-06-07]
 
 ### Release Notes
@@ -50,7 +59,6 @@ time before a new metric is included by the plugin.
 - [#1316](https://github.com/influxdata/telegraf/pull/1316): Removed leaked "database" tag on redis metrics. Thanks @PierreF!
 - [#1323](https://github.com/influxdata/telegraf/issues/1323): Processes plugin: fix potential error with /proc/net/stat directory.
 - [#1322](https://github.com/influxdata/telegraf/issues/1322): Fix rare RHEL 5.2 panic in gopsutil diskio gathering function.
-- [#1336](https://github.com/influxdata/telegraf/issues/1336): Fixed incorrect prometheus metrics source selection
 
 ## v0.13.1 [2016-05-24]
 

plugins/inputs/exec/exec.go

@@ -177,8 +177,12 @@ func (e *Exec) Gather(acc telegraf.Accumulator) error {
 			// There were matches, so we'll append each match together with
 			// the arguments to the commands slice
 			for _, match := range matches {
-				commands = append(
-					commands, strings.Join([]string{match, cmdAndArgs[1]}, " "))
+				if len(cmdAndArgs) == 1 {
+					commands = append(commands, match)
+				} else {
+					commands = append(commands,
+						strings.Join([]string{match, cmdAndArgs[1]}, " "))
+				}
 			}
 		}
 	}