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bash pipe race condition
- From: Matthew McGIllis <matthew at mcgillis dot org>
- To: cygwin at cygwin dot com
- Date: Mon, 2 Oct 2017 18:06:17 -0700
- Subject: bash pipe race condition
- Authentication-results: sourceware.org; auth=none
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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