private static async Task RedirectionToFileAsync()
{
var tempFile = Path.GetTempFileName();
var si = new ChildProcessStartInfo("env")
{
ExtraEnvironmentVariables = new Dictionary <string, string> {
{ "A", "A" }
},
StdOutputRedirection = OutputRedirection.File,
StdErrorRedirection = OutputRedirection.File,
StdOutputFile = tempFile,
StdErrorFile = tempFile,
};
using (var p = ChildProcess.Start(si))
{
await p.WaitForExitAsync();
}
// LANG=C.UTF-8
// ...
Console.WriteLine(File.ReadAllText(tempFile));
File.Delete(tempFile);
}
private static async Task RedirectionToFileAsync()
{
var tempFile = Path.GetTempFileName();
var si = new ChildProcessStartInfo("cmd", "/C", "set")
{
ExtraEnvironmentVariables = new Dictionary <string, string> {
{ "A", "A" }
},
StdOutputRedirection = OutputRedirection.File,
StdErrorRedirection = OutputRedirection.File,
StdOutputFile = tempFile,
StdErrorFile = tempFile,
Flags = ChildProcessFlags.UseCustomCodePage,
CodePage = Encoding.Default.CodePage, // UTF-8 on .NET Core
};
using (var p = ChildProcess.Start(si))
{
await p.WaitForExitAsync();
}
// A=A
// ALLUSERSPROFILE=C:\ProgramData
// ...
Console.WriteLine(File.ReadAllText(tempFile));
File.Delete(tempFile);
}
static async Task SpawnCmdAsync()
{
var si = new ChildProcessStartInfo("sleep", "3s");
using var p = ChildProcess.Start(si);
await p.WaitForExitAsync();
}
// Truely asynchronous WaitForExitAsync: WaitForExitAsync does not consume a thread-pool thread.
// You will not need a dedicated thread for handling a child process.
// You can handle more processes than the number of threads.
private static async Task WaitForExitAsync()
{
const int N = 128;
var stopWatch = Stopwatch.StartNew();
var tasks = new Task[N];
for (int i = 0; i < N; i++)
{
tasks[i] = SpawnCmdAsync();
}
// Spawned 128 processes.
// The 128 processes have exited.
// Elapsed Time: 3367 ms
Console.WriteLine("Spawned {0} processes.", N);
await Task.WhenAll(tasks);
Console.WriteLine("The {0} processes have exited.", N);
Console.WriteLine("Elapsed Time: {0} ms", stopWatch.ElapsedMilliseconds);
async Task SpawnCmdAsync()
{
var si = new ChildProcessStartInfo("cmd", "/C", "timeout", "3")
{
StdInputRedirection = InputRedirection.ParentInput,
StdOutputRedirection = OutputRedirection.NullDevice,
};
using (var p = ChildProcess.Start(si))
{
await p.WaitForExitAsync();
}
}
}
static async Task SpawnCmdAsync()
{
var si = new ChildProcessStartInfo("sleep", "3s")
{
StdInputRedirection = InputRedirection.ParentInput,
StdOutputRedirection = OutputRedirection.NullDevice,
};
using var p = ChildProcess.Start(si);
await p.WaitForExitAsync();
}
static async Task SpawnCmdAsync(int i)
{
var si = new ChildProcessStartInfo("waitfor", "/T", "3", $"pause{i}")
{
StdInputRedirection = InputRedirection.ParentInput,
StdOutputRedirection = OutputRedirection.NullDevice,
Flags = ChildProcessFlags.AttachToCurrentConsole,
};
using var p = ChildProcess.Start(si);
await p.WaitForExitAsync();
}
private static async Task RedirectionToFileAsync()
{
var si = new ChildProcessStartInfo("cmd", "/C", "set")
{
StdOutputRedirection = OutputRedirection.File,
StdOutputFile = "env.txt",
};
using (var p = ChildProcess.Start(si))
{
await p.WaitForExitAsync();
}
// ALLUSERSPROFILE=C:\ProgramData
// ...
Console.WriteLine(File.ReadAllText("env.txt"));
}
private static async Task BasicAsync()
{
var si = new ChildProcessStartInfo("cmd", "/C", "echo", "foo")
{
StdOutputRedirection = OutputRedirection.OutputPipe,
};
using var p = ChildProcess.Start(si);
using (var sr = new StreamReader(p.StandardOutput !))
{
// "foo"
Console.Write(await sr.ReadToEndAsync());
}
await p.WaitForExitAsync();
// ExitCode: 0
Console.WriteLine("ExitCode: {0}", p.ExitCode);
}
private static async Task RedirectionToFileAsync()
{
var tempFile = Path.GetTempFileName();
var si = new ChildProcessStartInfo("ls", "/")
{
StdOutputRedirection = OutputRedirection.File,
StdOutputFile = tempFile,
};
using (var p = ChildProcess.Start(si))
{
await p.WaitForExitAsync();
}
// bin
// boot
// ...
Console.WriteLine(File.ReadAllText(tempFile));
File.Delete(tempFile);
}
// Truely asynchronous WaitForExitAsync: WaitForExitAsync does not consume a thread-pool thread.
// You will not need a dedicated thread for handling a child process.
// You can handle more processes than the number of threads.
private static async Task WaitForExitAsync()
{
const int N = 128;
var stopWatch = Stopwatch.StartNew();
var tasks = new Task[N];
for (int i = 0; i < N; i++)
{
tasks[i] = SpawnCmdAsync();
}
// Spawned 128 processes.
// The 128 processes have exited.
// Elapsed Time: 3367 ms
Console.WriteLine("Spawned {0} processes.", N);
await Task.WhenAll(tasks);
Console.WriteLine("The {0} processes have exited.", N);
Console.WriteLine("Elapsed Time: {0} ms", stopWatch.ElapsedMilliseconds);
async Task SpawnCmdAsync()
{
// Using timeout because Windows does not have a handy sleep command.
// (`powershell -NoProfile -Command Sleep 3` is not an option because
// it takes ~200 ms to boot.)
//
// This is super racy because these N timeout processes simultaneously
// attempts to perform PeekConsoleInput followed by ReadConsoleInput.
// When a console input arrives, some processes will get stuck in ReadConsoleInput.
var si = new ChildProcessStartInfo("timeout", "3")
{
StdInputRedirection = InputRedirection.ParentInput,
StdOutputRedirection = OutputRedirection.NullDevice,
};
using var p = ChildProcess.Start(si);
await p.WaitForExitAsync();
}
}
