Okay - I found out the issue and solution - the output-port has to be explicitly closed in order for the pipe to know there are no more data coming through. I guess I misconstrue the meaning of "The ports do not need to be explicitly closed" in <a href="http://docs.plt-scheme.org/reference/pipeports.html#(def._((quote._~23~25kernel)._make-pipe))">http://docs.plt-scheme.org/reference/pipeports.html#(def._((quote._~23~25kernel)._make-pipe))</a> . Problem solved - thanks. yc <div class="gmail_quote">On Thu, Sep 3, 2009 at 8:47 PM, YC <<a href="mailto:yinso.chen@gmail.com">yinso.chen@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Update - I was able to isolate the problem to just the pipe. <div style="margin-left: 40px;">(define-values (in out) (make-pipe #f)) (write-bytes #"this is a test" out) (read-bytes 14 in) ;; reads out #"this is a test" (read-bytes 1 in) ;; hangs. </div> It seems that unlike regular input-port, pipe does not produce #<eof> in this situation. How can I make the pipe generate #<eof>? Thanks, yc<div> <div></div><div class="h5"> <div class="gmail_quote"> On Thu, Sep 3, 2009 at 7:37 PM, YC <<a href="mailto:yinso.chen@gmail.com" target="_blank">yinso.chen@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Hi - I am trying to pipe a gzipped file and it seems to hang at the end when I am trying to read the data. It's unclear to me why it hangs at the end (I observed this by seeing it hangs immediately with small files, read quite a bit of data with medium files, and read lots of data with large files before it hangs), and hopefully others can see what I am missing here. Thanks, yc ;; gzip.ss #lang scheme/base (require file/gunzip file/gzip mzlib/trace scheme/port) (define (open-gzip-file path) (let-values (((in out) (make-pipe-with-specials #f path))) (thread (lambda () (call-with-input-file path (lambda (in) (gunzip-through-ports in out))))) in)) (define (read-bytes* num in) (read-bytes num in)) (trace read-bytes*) (define (reader in) (let loop ((b (read-bytes* 4096 in))) (if (eof-object? b) ;; (reverse acc) (void) (loop (read-bytes* 4096 in))))) (provide reader open-gzip-file) ;; test ;; uncomment and run the two lines below in REPL ;; (require "gzip.ss") ;; (reader (open-gzip-file path-to-gzipped-file)) ;; observe the it eventually hangs on calling read-bytes*. </blockquote></div> </div></div></blockquote></div>