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From: Matthew McGIllis <matthew@mcgillis.org>
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Subject: bash pipe race condition
Message-Id: <B05F4669-BE32-4C5C-B366-555CE37A6761@mcgillis.org>
Date: Tue, 03 Oct 2017 01:06:00 -0000
To: cygwin@cygwin.com
X-SW-Source: 2017-10/txt/msg00020.txt.bz2

Windows 7 Service Pack 1
64-Bit Operating System

Cygwin
$ uname -r=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20
2.9.0(0.318/5/3)
$ uname -m=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20
x86_64=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20

The basic issue is in a normal windows command shell if I do

$ .\input.exe | .\simple.exe=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
line1
line2

If I use the same code from bash I get:

$ ./input.exe | ./simple.exe
line1
<=E2=80=94=E2=80=94 Hangs indefinitely until you kill it or ctrl-c

Some how if input has a delay between its line output then things will get =
hung, if you remove the sleep from the input things work, add the sleep in =
it fails.


input.exe is generate from input.vb using: vbc input.vb

 input.vb file:
Module input
  Sub Main()
    Console.Out.WriteLine("line1")
    Threading.Thread.Sleep(2000)
    Console.Out.WriteLine("line2")
  End Sub
End Module

simple.exe is generated from simple.vb using: vbc simple.vb

simple.vb file:
Module simple
  Sub Main()
    Dim line As String
    line =3D Console.In.ReadLine()
    Do Until line Is Nothing
      Console.Out.WriteLine(line)
      line =3D Console.In.ReadLine()
    Loop
  End Sub
End Module

Microsoft (R) Visual Basic Compiler version 11.0.50938.18408

The above problem was found when attempting to use cygwin perl using IPC::O=
pen2 to control stdin and stdout of a VB program. So this may not be a bash=
 specific issue but some sort of generic pipe issue in cygwin.
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