hi Daniel, thanks for reply! I tried guile-lib just now, it's nice. I'll use it.
Besides, do you think pipe is the proper way to implement "sed" function? Or it's better to implement a module with pure Guile? On Wed, Jun 13, 2012 at 3:19 PM, Daniel Hartwig <mand...@gmail.com> wrote: > On 13 June 2012 14:55, Nala Ginrut <nalagin...@gmail.com> wrote: >> hi folks! I'm on my trip and inconvenient to meet you guys on IRC. >> Things gonna be normal next month. >> >> Anyway, there's a problem for you. >> I'm trying to write a simple wrapper for "sed" with our popen module: >> --------------code------------ >> (use-modules (ice-9 popen) (rnrs)) >> (define (sed pattern str) >> (let ((p (open-input-output-pipe (string-append "sed " pattern)))) >> (display str p) >> (get-string-all p))) >> ----------------end------------- >> >> I expect it run like this: >> ----------------------- >> (sed "s:a:b:g" "abcabc") >> ==> "bbcbbc" >> ----------------------- >> >> But it halts that I have to interrupt. >> Is it accepted? >> > > The sed program may be expecting a newline, or waiting for EOF or a > full buffer before producing it's output. Some users have had trouble > with this in the past, because you can not send EOF to one end of the > pipe without closing the other. > > One way around this to use run-with-pipe from the guile-lib module (os > process). This returns two separate pipe objects for input and > output, thus you can close/EOF one and continue to use the other. > Many filter programs do not flush their output until their input EOFs, > which is why your solution using 'echo -n' works. > > See this thread for a short discussion: > > http://lists.gnu.org/archive/html/guile-user/2012-02/msg00066.html > > Updating guile to support closing one end of the pipe is long off on my TODO. >
