You shouldnt need to explicitly call eof or close
On Tuesday, June 3, 2014, Bob Nnamtrop <[email protected]> wrote:
> OK. I've got something that works, but it seems necessary to add a dummy
> write and then strip it out at the end.
>
> julia> function return_stdout(f::Function)
> stdout_orig = STDOUT
> rd, wr = redirect_stdout()
> print("_") # dummy write so eof(rd) doesn't block when f()
> has no output
> f()
> close(wr)
> eof(rd)
> close(rd)
> out = readall(rd)
> out = replace(out, "_", "", 1)
> redirect_stdout(stdout_orig)
> out
> end
> return_stdout (generic function with 1 method)
>
> julia> print("Case 1: "*return_stdout(()->println("Some output")))
> Case 1: Some output
>
> julia> print("Case 2: "*return_stdout(()->run(`echo Some output`)))
> Case 2: Some output
>
> julia> print("Case 3: "*return_stdout(()->nothing))
> Case 3:
> julia>
>
> Note that if you comment out the print("_") line then it will block in
> Case 3. Seems strange to me that this is necessary, but at least it works.
> Also, the ordering of the close statements and eof statement is important
> and not obvious from the docs. Does this look like a good way to do this?
>
> Thanks,
> Bob
>
>
> On Tue, Jun 3, 2014 at 11:35 AM, Jameson Nash <[email protected]> wrote:
>
> readall or readbytes
>
> The number of bytes that can be read without a syscall (nb_available) is
> not a good test of how much can be gotten from a syscall. However, after
> eof returns true, then nb_available is the upper bound on the data that can
> be read.
>
>
>
> On Tuesday, June 3, 2014, Bob Nnamtrop <[email protected]> wrote:
>
> OK, but I still cannot seem to find out if there is output available. Try:
>
> julia> function test_redirect(f::Function)
> stdout_orig = STDOUT
> rd, wr = redirect_stdout()
> f()
> close(wr)
> nb = nb_available(rd)
> redirect_stdout(stdout_orig)
> nb
> end
> test_redirect (generic function with 1 method)
>
> julia> println(test_redirect(()->println("Some output")))
> 0
>
> julia> println(test_redirect(()->run(`echo Some output`)))
> 0
>
> julia> println(test_redirect(()->nothing))
> 0
>
> So whether there is anything there or not nb_available returns 0?
>
> What do you recommend instead of readavailable?
> Bob
>
>
> On Tue, Jun 3, 2014 at 9:00 AM, Jameson Nash <[email protected]> wrote:
>
> You need to close the pipe you called stdin before trying to read from
> stdout. Otherwise, the answers you get are correct -- readavailable can
> return whatever it wants. It is not know if all data written to the pipe is
> available until the write end is closed, and the read end sees an eof
>
> readavailable is a badly defined function. Don't use it.
>
> eof needs to block if there is no data available since it can't answer
> that question until the stream is closed (eof) or there is more data (!eof)
>
>
>
> On Tuesday, June 3, 2014, Bob Nnamtrop <[email protected]> wrote:
>
> I am having an issue detecting if STDOUT is empty after I redirect it. I'm
> using an external C program may or may not write to STDOUT. Thus, I need to
> know if there is anything there before I readavailable from it (since
> readavailable blocks if the p
>
>
