bash pipe race condition

bash pipe race condition

[Matthew McGIllis]

Windows 7 Service Pack 1
64-Bit Operating System

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

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

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

If I use the same code from bash I get:

$ ./input.exe | ./simple.exe
line1
<—— 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 = Console.In.ReadLine()
    Do Until line Is Nothing
      Console.Out.WriteLine(line)
      line = 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::Open2 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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Re: bash pipe race condition

[cyg Simple]

On 10/2/2017 9:06 PM, Matthew McGIllis wrote:

> 
> If I use the same code from bash I get:
> 
> $ ./input.exe | ./simple.exe
> line1
> <—— 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 = Console.In.ReadLine()
>     Do Until line Is Nothing
>       Console.Out.WriteLine(line)
>       line = 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::Open2 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.

It is a known issue of the PTY emulation between a Cygwin runtime and a
Windows runtime enabled app.  It just cannot be fixed.  You're even
lucky that it works in the Windows command shell.  Either convert
simple.vb to simple.c and use Cygwin's gcc to build it or create a
Windows runtime version of input.exe.

-- 
cyg Simple

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Re: bash pipe race condition

[Kaz Kylheku]

On 03.10.2017 05:56, cyg Simple wrote:
> On 10/2/2017 9:06 PM, Matthew McGIllis wrote:
>> If I use the same code from bash I get:
>> 
>> $ ./input.exe | ./simple.exe
>> line1
>> <—— 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
[ ... ]
> 
> It is a known issue of the PTY emulation between a Cygwin runtime and a
> Windows runtime enabled app.  It just cannot be fixed.  You're even
> lucky that it works in the Windows command shell.

Lucky? Are VB console apps known to have unreliable piping when
used from the Windows command processor?

> Either convert
> simple.vb to simple.c and use Cygwin's gcc to build it or create a
> Windows runtime version of input.exe.

Isn't that what "input.exe is generate[d] from input.vb using: vbc 
input.vb"
is referring to?


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Re: bash pipe race condition

[cyg Simple]

On 10/3/2017 11:39 PM, Kaz Kylheku wrote:
> On 03.10.2017 05:56, cyg Simple wrote:
>> On 10/2/2017 9:06 PM, Matthew McGIllis wrote:
>>> If I use the same code from bash I get:
>>>
>>> $ ./input.exe | ./simple.exe
>>> line1
>>> <—— 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
> [ ... ]
>>
>> It is a known issue of the PTY emulation between a Cygwin runtime and a
>> Windows runtime enabled app.  It just cannot be fixed.  You're even
>> lucky that it works in the Windows command shell.
> 
> Lucky? Are VB console apps known to have unreliable piping when
> used from the Windows command processor?
> 
>> Either convert
>> simple.vb to simple.c and use Cygwin's gcc to build it or create a
>> Windows runtime version of input.exe.
> 
> Isn't that what "input.exe is generate[d] from input.vb using: vbc
> input.vb"
> is referring to?

Oh, yes, sorry I missed that.  Still an issue with PTY and cannot be
fixed regardless without creating a C program of both.  Straight console
on the stdin and stdout channels might work with the C runtime with MS
runtime but should be Cygwin runtime when using Cygwin.

-- 
cyg Simple

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