diff --git a/src/lib/io/pipe.go b/src/lib/io/pipe.go
index 5f9e7a4..1a443dd 100644
--- a/src/lib/io/pipe.go
+++ b/src/lib/io/pipe.go
@@ -21,7 +21,9 @@
 // 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 @@
 			p.wpend = <-p.cr;
 		}
 		if p.wpend == nil {
-			return 0, nil;
+			return 0, p.werr;
 		}
 		p.wtot = 0;
 	}
@@ -70,7 +72,7 @@
 		return 0, os.EINVAL;
 	}
 	if p.rclosed {
-		return 0, os.EPIPE;
+		return 0, p.rerr;
 	}
 
 	// Send data to reader.
@@ -81,29 +83,34 @@
 	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 @@
 //  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;
 }