Use C locale when running sadf (#2690)

fixes #1911

plugins/inputs/sysstat/sysstat.go

@@ -210,11 +210,37 @@ func (s *Sysstat) collect() error {
 	return nil
 }
 
+func filterEnviron(env []string, prefix string) []string {
+	newenv := env[:0]
+	for _, envvar := range env {
+		if !strings.HasPrefix(envvar, prefix) {
+			newenv = append(newenv, envvar)
+		}
+	}
+	return newenv
+}
+
+// Return the Cmd with its environment configured to use the C locale
+func withCLocale(cmd *exec.Cmd) *exec.Cmd {
+	var env []string
+	if cmd.Env != nil {
+		env = cmd.Env
+	} else {
+		env = os.Environ()
+	}
+	env = filterEnviron(env, "LANG")
+	env = filterEnviron(env, "LC_")
+	env = append(env, "LANG=C")
+	cmd.Env = env
+	return cmd
+}
+
 // parse runs Sadf on the previously saved tmpFile:
 //    Sadf -p -- -p <option> tmpFile
 // and parses the output to add it to the telegraf.Accumulator acc.
 func (s *Sysstat) parse(acc telegraf.Accumulator, option string, ts time.Time) error {
 	cmd := execCommand(s.Sadf, s.sadfOptions(option)...)
+	cmd = withCLocale(cmd)
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {
 		return err

plugins/inputs/sysstat/sysstat_interval_test.go

@@ -15,6 +15,9 @@ import (
 // run with -race option, because in that scenario interval between the two
 // Gather calls is greater than wantedInterval.
 func TestInterval(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test with sleep in short mode.")
+	}
 	// overwriting exec commands with mock commands
 	execCommand = fakeExecCommand
 	defer func() { execCommand = exec.Command }()