关于从F#运行进程我有一个奇怪的行为.我的基本问题是要运行的Graphviz的dot.exe一个生成的图形和可视化它.
当我将图表限制为小时,一切正常.但是对于更大的图表,它挂在特定的线上.我很好奇为什么会这样,所以也许我可以解决我的问题.我为此目的创建了一个MVCE.
我有2个控制台程序.一个是模拟器dot.exe,在那里我将展示输入,并期望.jpg.这个版本只是输出10次输出到输出的块:
// Learn more about F# at http://fsharp.org
// See the 'F# Tutorial' project for more help.
open System
open System.IO
[<EntryPoint>]
let main argv =
let bufferSize = 4096
let mutable buffer : char [] = Array.zeroCreate bufferSize
// it repeats in 4096 blocks, but it doesn't matter. It's a simulation of outputing 10 times amount output.
while Console.In.ReadBlock(buffer, 0, bufferSize) <> 0 do
for i in 1 .. 10 do
Console.Out.WriteLine(buffer)
0 // return an integer exit code
所以我有一个.exe名为C:\Users\MyUserName\Documents\Visual Studio 2015\Projects\ProcessInputOutputMVCE\EchoExe\bin\Debug\EchoExe.exeThan的另一个控制台项目,它使用它:
// Learn more about F# at http://fsharp.org
// See the 'F# Tutorial' project for more help.
open System.IO
[<EntryPoint>]
let main argv =
let si =
new System.Diagnostics.ProcessStartInfo(@"C:\Users\MyUserName\Documents\Visual Studio 2015\Projects\ProcessInputOutputMVCE\EchoExe\bin\Debug\EchoExe.exe", "",
// from Fake's Process handling
#if FX_WINDOWSTLE
WindowStyle = ProcessWindowStyle.Hidden,
#else
CreateNoWindow = true,
#endif
UseShellExecute = false,
RedirectStandardOutput = true,
RedirectStandardError = true,
RedirectStandardInput = true)
use p = new System.Diagnostics.Process()
p.StartInfo <- si
if p.Start() then
let input =
Seq.replicate 3000 "aaaa"
|> String.concat "\n"
p.StandardInput.Write input
// hangs on Flush()
p.StandardInput.Flush()
p.StandardInput.Close()
use outTxt = File.Create "out.txt"
p.StandardOutput.BaseStream.CopyTo outTxt
// double WaitForExit because of https://msdn.microsoft.com/en-us/library/system.diagnostics.process.standardoutput(v=vs.110).aspx
// saying first WaitForExit() waits for StandardOutput. Next is needed for the whole process.
p.WaitForExit()
p.WaitForExit()
0 // return an integer exit code
哪个挂在上面p.StandardInput.Flush().除非我将输入音量更改为Seq.replicate 300 "aaaa".为什么它的工作方式不同？
Process.StandardOutput的引用声明读取StandardOutput和子进程在同一时间写入该流可能会导致死锁.在这种情况下,谁是儿童过程？是我的p.StandardInput.Write input吗？
其他可能的僵局将是
从标准输出和标准错误流中读取所有文本.
但我不是在读错误流.无论如何它建议用异步处理输入/输出所以我有一个以下版本:
// same as before
...
if p.Start() then
let rec writeIndefinitely (rows: string list) =
async {
if rows.Length = 0 then
()
else
do! Async.AwaitTask (p.StandardInput.WriteLineAsync rows.Head)
p.StandardInput.Flush()
do! writeIndefinitely rows.Tail
}
let inputTaskContinuation =
Seq.replicate 3000 "aaaa"
|> Seq.toList
|> writeIndefinitely
Async.Start (async {
do! inputTaskContinuation
p.StandardInput.Close()
}
)
let bufferSize = 4096
let mutable buffer : char array = Array.zeroCreate bufferSize
use outTxt = File.CreateText "out.txt"
let rec readIndefinitely() =
async {
let! readBytes = Async.AwaitTask (p.StandardOutput.ReadAsync (buffer, 0, bufferSize))
if readBytes <> 0 then
outTxt.Write (buffer, 0, buffer.Length)
outTxt.Flush()
do! readIndefinitely()
}
Async.Start (async {
do! readIndefinitely()
p.StandardOutput.Close()
})
// with that it throws "Cannot mix synchronous and asynchronous operation on process stream." on let! readBytes = Async.AwaitTask (p.StandardOutput.ReadAsync (buffer, 0, bufferSize))
//p.BeginOutputReadLine()
p.WaitForExit()
// using dot.exe, it hangs on the second WaitForExit()
p.WaitForExit()
哪个不挂,写道out.txt.除了真正的代码使用dot.exe.这是异步的.为什么会抛出异常p.BeginOutputReadLine()？
一些试验后,整个异步出可以留p.StandardOutput.BaseStream.CopyTo outTxt在那里outTxt是File.Create不是File.CreateText.只有异步输入对同步输入处理才是正确的.这很奇怪.
把它们加起来.如果我有异步输入处理,它工作正常(除非dot.exe,但如果我弄清楚,也许我也可以修复它),如果它有同步输入处理,它取决于输入的大小.(300件作品,3000件没有)为什么？
更新
由于我真的不需要重定向标准错误,我已经删除了RedirectStandardError = true.这解决了这个神秘的dot.exe问题.
我认为这里的僵局如下:
没有必要使用完全异步的代码.我认为可行的方法是在编写点之前将其写入dot的stdin,并在再次写入之前读到dot的stdout.