Add DialWithDebugOutput to log commands.

debug.go

@@ -0,0 +1,21 @@
+package ftp
+
+import "io"
+
+type debugWrapper struct {
+	conn io.ReadWriteCloser
+	io.Reader
+	io.Writer
+}
+
+func newDebugWrapper(conn io.ReadWriteCloser, w io.Writer) io.ReadWriteCloser {
+	return &debugWrapper{
+		Reader: io.TeeReader(conn, w),
+		Writer: io.MultiWriter(w, conn),
+		conn:   conn,
+	}
+}
+
+func (w *debugWrapper) Close() error {
+	return w.conn.Close()
+}

ftp.go

@@ -53,6 +53,7 @@ type dialOptions struct {
 	conn        net.Conn
 	disableEPSV bool
 	location    *time.Location
+	debugOutput io.Writer
 }
 
 // Entry describes a file and is returned by List().
@@ -100,10 +101,15 @@ func DialWithOptions(addr string, options ...DialOption) (*ServerConn, error) {
 	// If we use the domain name, we might not resolve to the same IP.
 	remoteAddr := tconn.RemoteAddr().(*net.TCPAddr)
 
+	var sourceConn io.ReadWriteCloser = tconn
+	if do.debugOutput != nil {
+		sourceConn = newDebugWrapper(tconn, do.debugOutput)
+	}
+
 	c := &ServerConn{
 		options:  do,
 		features: make(map[string]string),
-		conn:     textproto.NewConn(tconn),
+		conn:     textproto.NewConn(sourceConn),
 		host:     remoteAddr.IP.String(),
 	}
 
@@ -178,6 +184,14 @@ func DialWithTLS(tlsConfig tls.Config) DialOption {
 	}}
 }
 
+// DialWithDebugOutput returns a DialOption that configures the ServerConn to write to the Writer
+// everything it reads from the server
+func DialWithDebugOutput(w io.Writer) DialOption {
+	return DialOption{func(do *dialOptions) {
+		do.debugOutput = w
+	}}
+}
+
 // Connect is an alias to Dial, for backward compatibility
 func Connect(addr string) (*ServerConn, error) {
 	return Dial(addr)