diff --git a/src/lib/io/pipe.go b/src/lib/io/pipe.go
index 5f9e7a488c0..1a443ddcec2 100644
--- a/src/lib/io/pipe.go
+++ b/src/lib/io/pipe.go
@@ -21,7 +21,9 @@ type pipeReturn struct {
 // Shared pipe structure.
 type pipe struct {
 	rclosed bool;		// Read end closed?
+	rerr os.Error;		// Error supplied to CloseReader
 	wclosed bool;		// Write end closed?
+	werr os.Error;		// Error supplied to CloseWriter
 	wpend []byte;		// Written data waiting to be read.
 	wtot int;		// Bytes consumed so far in current write.
 	cr chan []byte;		// Write sends data here...
@@ -39,7 +41,7 @@ func (p *pipe) Read(data []byte) (n int, err os.Error) {
 			p.wpend = <-p.cr;
 		}
 		if p.wpend == nil {
-			return 0, nil;
+			return 0, p.werr;
 		}
 		p.wtot = 0;
 	}
@@ -70,7 +72,7 @@ func (p *pipe) Write(data []byte) (n int, err os.Error) {
 		return 0, os.EINVAL;
 	}
 	if p.rclosed {
-		return 0, os.EPIPE;
+		return 0, p.rerr;
 	}
 
 	// Send data to reader.
@@ -81,29 +83,34 @@ func (p *pipe) Write(data []byte) (n int, err os.Error) {
 	return res.n, res.err;
 }
 
-func (p *pipe) CloseReader() os.Error {
+func (p *pipe) CloseReader(rerr os.Error) os.Error {
 	if p == nil || p.rclosed {
 		return os.EINVAL;
 	}
 
 	// Stop any future writes.
 	p.rclosed = true;
+	if rerr == nil {
+		rerr = os.EPIPE;
+	}
+	p.rerr = rerr;
 
 	// Stop the current write.
 	if !p.wclosed {
-		p.cw <- pipeReturn{p.wtot, os.EPIPE};
+		p.cw <- pipeReturn{p.wtot, rerr};
 	}
 
 	return nil;
 }
 
-func (p *pipe) CloseWriter() os.Error {
+func (p *pipe) CloseWriter(werr os.Error) os.Error {
 	if p == nil || p.wclosed {
 		return os.EINVAL;
 	}
 
 	// Stop any future reads.
 	p.wclosed = true;
+	p.werr = werr;
 
 	// Stop the current read.
 	if !p.rclosed {
@@ -121,70 +128,98 @@ func (p *pipe) CloseWriter() os.Error {
 //  2.  Clients cannot use interface conversions on the
 //      read end to find the Write method, and vice versa.
 
-// Read half of pipe.
-type pipeRead struct {
+// A PipeReader is the read half of a pipe.
+type PipeReader struct {
 	lock sync.Mutex;
 	p *pipe;
 }
 
-func (r *pipeRead) Read(data []byte) (n int, err os.Error) {
+// Read implements the standard Read interface:
+// it reads data from the pipe, blocking until a writer
+// arrives or the write end is closed.
+// If the write end is closed with an error, that error is
+// returned as err; otherwise err is nil.
+func (r *PipeReader) Read(data []byte) (n int, err os.Error) {
 	r.lock.Lock();
 	defer r.lock.Unlock();
 
 	return r.p.Read(data);
 }
 
-func (r *pipeRead) Close() os.Error {
+// Close closes the reader; subsequent writes to the
+// write half of the pipe will return the error os.EPIPE.
+func (r *PipeReader) Close() os.Error {
 	r.lock.Lock();
 	defer r.lock.Unlock();
 
-	return r.p.CloseReader();
+	return r.p.CloseReader(nil);
 }
 
-func (r *pipeRead) finish() {
+// CloseWithError closes the reader; subsequent writes
+// to the write half of the pipe will return the error rerr.
+func (r *PipeReader) CloseWithError(rerr os.Error) os.Error {
+	r.lock.Lock();
+	defer r.lock.Unlock();
+
+	return r.p.CloseReader(rerr);
+}
+
+func (r *PipeReader) finish() {
 	r.Close();
 }
 
 // Write half of pipe.
-type pipeWrite struct {
+type PipeWriter struct {
 	lock sync.Mutex;
 	p *pipe;
 }
 
-func (w *pipeWrite) Write(data []byte) (n int, err os.Error) {
+// Write implements the standard Write interface:
+// it writes data to the pipe, blocking until readers
+// have consumed all the data or the read end is closed.
+// If the read end is closed with an error, that err is
+// returned as err; otherwise err is os.EPIPE.
+func (w *PipeWriter) Write(data []byte) (n int, err os.Error) {
 	w.lock.Lock();
 	defer w.lock.Unlock();
 
 	return w.p.Write(data);
 }
 
-func (w *pipeWrite) Close() os.Error {
+// Close closes the writer; subsequent reads from the
+// read half of the pipe will return no bytes and a nil error.
+func (w *PipeWriter) Close() os.Error {
 	w.lock.Lock();
 	defer w.lock.Unlock();
 
-	return w.p.CloseWriter();
+	return w.p.CloseWriter(nil);
 }
 
-func (w *pipeWrite) finish() {
+// CloseWithError closes the writer; subsequent reads from the
+// read half of the pipe will return no bytes and the error werr.
+func (w *PipeWriter) CloseWithError(werr os.Error) os.Error {
+	w.lock.Lock();
+	defer w.lock.Unlock();
+
+	return w.p.CloseWriter(werr);
+}
+
+func (w *PipeWriter) finish() {
 	w.Close();
 }
 
 // Pipe creates a synchronous in-memory pipe.
-// Used to connect code expecting an io.Reader
+// It can be used to connect code expecting an io.Reader
 // with code expecting an io.Writer.
-//
-// Reads on one end are matched by writes on the other.
-// Writes don't complete until all the data has been
-// written or the read end is closed.  Reads return
-// any available data or block until the next write
-// or the write end is closed.
-func Pipe() (io.ReadCloser, io.WriteCloser) {
+// Reads on one end are matched with writes on the other,
+// copying data directly between the two; there is no internal buffering.
+func Pipe() (*PipeReader, *PipeWriter) {
 	p := new(pipe);
 	p.cr = make(chan []byte, 1);
 	p.cw = make(chan pipeReturn, 1);
-	r := new(pipeRead);
+	r := new(PipeReader);
 	r.p = p;
-	w := new(pipeWrite);
+	w := new(PipeWriter);
 	w.p = p;
 	return r, w;
 }
diff --git a/src/lib/io/pipe_test.go b/src/lib/io/pipe_test.go
index 3df66962854..277f445250c 100644
--- a/src/lib/io/pipe_test.go
+++ b/src/lib/io/pipe_test.go
@@ -5,6 +5,7 @@
 package io
 
 import (
+	"fmt";
 	"io";
 	"os";
 	"testing";
@@ -132,72 +133,93 @@ func TestPipe3(t *testing.T) {
 
 // Test read after/before writer close.
 
-func delayClose(t *testing.T, cl Closer, ch chan int) {
-	time.Sleep(1000*1000);	// 1 ms
-	if err := cl.Close(); err != nil {
+type closer interface {
+	CloseWithError(os.Error) os.Error;
+	Close() os.Error;
+}
+
+type pipeTest struct {
+	async bool;
+	err os.Error;
+	closeWithError bool;
+}
+
+func (p pipeTest) String() string {
+	return fmt.Sprintf("async=%v err=%v closeWithError=%v", p.async, p.err, p.closeWithError);
+}
+
+var pipeTests = []pipeTest {
+	pipeTest{ true, nil, false },
+	pipeTest{ true, nil, true },
+	pipeTest{ true, io.ErrShortWrite, true },
+	pipeTest{ false, nil, false },
+	pipeTest{ false, nil, true },
+	pipeTest{ false, io.ErrShortWrite, true },
+}
+
+func delayClose(t *testing.T, cl closer, ch chan int, tt pipeTest) {
+	time.Sleep(1e6);	// 1 ms
+	var err os.Error;
+	if tt.closeWithError {
+		err = cl.CloseWithError(tt.err);
+	} else {
+		err = cl.Close();
+	}
+	if err != nil {
 		t.Errorf("delayClose: %v", err);
 	}
 	ch <- 0;
 }
 
-func testPipeReadClose(t *testing.T, async bool) {
-	c := make(chan int, 1);
-	r, w := Pipe();
-	if async {
-		go delayClose(t, w, c);
-	} else {
-		delayClose(t, w, c);
-	}
-	var buf = make([]byte, 64);
-	n, err := r.Read(buf);
-	<-c;
-	if err != nil {
-		t.Errorf("read from closed pipe: %v", err);
-	}
-	if n != 0 {
-		t.Errorf("read on closed pipe returned %d", n);
-	}
-	if err = r.Close(); err != nil {
-		t.Errorf("r.Close: %v", err);
+func TestPipeReadClose(t *testing.T) {
+	for _, tt := range pipeTests {
+		c := make(chan int, 1);
+		r, w := Pipe();
+		if tt.async {
+			go delayClose(t, w, c, tt);
+		} else {
+			delayClose(t, w, c, tt);
+		}
+		var buf = make([]byte, 64);
+		n, err := r.Read(buf);
+		<-c;
+		if err != tt.err {
+			t.Errorf("read from closed pipe: %v want %v", err, tt.err);
+		}
+		if n != 0 {
+			t.Errorf("read on closed pipe returned %d", n);
+		}
+		if err = r.Close(); err != nil {
+			t.Errorf("r.Close: %v", err);
+		}
 	}
 }
 
 // Test write after/before reader close.
 
-func testPipeWriteClose(t *testing.T, async bool) {
-	c := make(chan int, 1);
-	r, w := Pipe();
-	if async {
-		go delayClose(t, r, c);
-	} else {
-		delayClose(t, r, c);
-	}
-	n, err := WriteString(w, "hello, world");
-	<-c;
-	if err != os.EPIPE {
-		t.Errorf("write on closed pipe: %v", err);
-	}
-	if n != 0 {
-		t.Errorf("write on closed pipe returned %d", n);
-	}
-	if err = w.Close(); err != nil {
-		t.Errorf("w.Close: %v", err);
+func TestPipeWriteClose(t *testing.T) {
+	for _, tt := range pipeTests {
+		c := make(chan int, 1);
+		r, w := Pipe();
+		if tt.async {
+			go delayClose(t, r, c, tt);
+		} else {
+			delayClose(t, r, c, tt);
+		}
+		n, err := WriteString(w, "hello, world");
+		<-c;
+		expect := tt.err;
+		if expect == nil {
+			expect = os.EPIPE;
+		}
+		if err != expect {
+			t.Errorf("write on closed pipe: %v want %v", err, expect);
+		}
+		if n != 0 {
+			t.Errorf("write on closed pipe returned %d", n);
+		}
+		if err = w.Close(); err != nil {
+			t.Errorf("w.Close: %v", err);
+		}
 	}
 }
-
-func TestPipeReadCloseAsync(t *testing.T) {
-	testPipeReadClose(t, true);
-}
-
-func TestPipeReadCloseSync(t *testing.T) {
-	testPipeReadClose(t, false);
-}
-
-func TestPipeWriteCloseAsync(t *testing.T) {
-	testPipeWriteClose(t, true);
-}
-
-func TestPipeWriteCloseSync(t *testing.T) {
-	testPipeWriteClose(t, false);
-}
-