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 pipe is empty). Here is some code to show the
issue (I redirect STDOUT and send nothing to it and try to check if there
is anything there):
julia> stdout_orig = STDOUT
TTY(open, 0 bytes waiting)
julia> stdout, stdin = redirect_stdout()
(Pipe(open, 0 bytes waiting),Pipe(open, 0 bytes waiting))
julia> if !eof(stdout)
out = readavailable(stdout)
end
This last command blocks on eof(stdout), which makes it worthless for this
purpose. Is it suppose to block when there is nothing in the Pipe? The help
for eof says "If the stream is not yet exhausted, this function will block
to wait for more data if necessary, and then return "false". " I'm not sure
how to interpret this. The behavior of eof seems like a bug to me.
So looking at the docs I figure I can use nb_available instead but it
doesn't seem to be reliable when the pipe is used by external programs. For
example (restarting julia):
julia> stdout, stdin = redirect_stdout()
(Pipe(open, 0 bytes waiting),Pipe(open, 0 bytes waiting))
julia> stdout, stdin = redirect_stdout()
(Pipe(open, 0 bytes waiting),Pipe(open, 0 bytes waiting))
julia> run(`echo Some output`)
julia> nb_available(stdout)
0
This should have returned 12. Adding flush_cstdio() doesn't help.
nb_available seems to work if you use julia programs to write to STDOUT but
not for external programs. Is this a bug?
Am I missing something?
Thanks,
Bob
ps Here is my version:
julia> versioninfo()
Julia Version 0.3.0-prerelease+3407
Commit 152b3d3 (2014-06-02 21:29 UTC)
Platform Info:
System: Darwin (x86_64-apple-darwin13.2.0)
CPU: Intel(R) Core(TM)2 Duo CPU T9550 @ 2.66GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY)
LAPACK: libopenblas
LIBM: libopenlibm
