[Caml-list] Unix.open_process "cat"

[Caml-list] Unix.open_process "cat"

[Martin Jambon]

Hello,

I would like to apply some external filters (e.g. cat, grep, sed, ...)
that will terminate successfully only if they reach an
end-of-file. For this I would like to use Unix.open_process, but I need to
close the output first (= the input of the command).
Is it legal to use close_out on the out_channel returned by
Unix.open_process, and later use Unix.close_process on the pair of
channels?

Here is my code (which seems to work):

#load "unix.cma"

let feed command data f =
  let (ic, oc) as channels = Unix.open_process command in
  output_string oc data;
  close_out oc;  (** <-- is this OK? **)
  (try
     while true do
       f (input_char ic)
     done
   with End_of_file -> ());
  match Unix.close_process channels with
      Unix.WEXITED 0 -> ()
    | _ -> invalid_arg ("feed: " ^ command)

let _ = feed "cat" "mouse" print_char



Martin

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Re: [Caml-list] Unix.open_process "cat"

[Olivier Andrieu]

 Martin Jambon [Sat, 15 May 2004]:
 > Hello,
 > 
 > I would like to apply some external filters (e.g. cat, grep, sed, ...)
 > that will terminate successfully only if they reach an
 > end-of-file. For this I would like to use Unix.open_process, but I need to
 > close the output first (= the input of the command).
 > Is it legal to use close_out on the out_channel returned by
 > Unix.open_process, and later use Unix.close_process on the pair of
 > channels?

Yes, Unix.close_process will call close_out on the channel again but
this is safe.

-- 
   Olivier

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