Extend Iptables interface with SaveInto

pkg/util/exec/exec.go

@@ -41,6 +41,8 @@ type Interface interface {
 // As more functionality is needed, this can grow.  Since Cmd is a struct, we will have
 // to replace fields with get/set method pairs.
 type Cmd interface {
+	// Run runs the command to the completion.
+	Run() error
 	// CombinedOutput runs the command and returns its combined standard output
 	// and standard error.  This follows the pattern of package os/exec.
 	CombinedOutput() ([]byte, error)
@@ -49,6 +51,7 @@ type Cmd interface {
 	SetDir(dir string)
 	SetStdin(in io.Reader)
 	SetStdout(out io.Writer)
+	SetStderr(out io.Writer)
 	// Stops the command by sending SIGTERM. It is not guaranteed the
 	// process will stop before this function returns. If the process is not
 	// responding, an internal timer function will send a SIGKILL to force
@@ -99,6 +102,15 @@ func (cmd *cmdWrapper) SetStdout(out io.Writer) {
 	cmd.Stdout = out
 }
 
+func (cmd *cmdWrapper) SetStderr(out io.Writer) {
+	cmd.Stderr = out
+}
+
+// Run is part of the Cmd interface.
+func (cmd *cmdWrapper) Run() error {
+	return (*osexec.Cmd)(cmd).Run()
+}
+
 // CombinedOutput is part of the Cmd interface.
 func (cmd *cmdWrapper) CombinedOutput() ([]byte, error) {
 	out, err := (*osexec.Cmd)(cmd).CombinedOutput()