使用 C# 捕获进程输出

Intro

很多时候我们可能会需要执行一段命令获取一个输出，遇到的比较典型的就是之前我们需要用 FFMpeg 实现视频的编码压缩水印等一系列操作，当时使用的是 FFMpegCore 这个类库，这个类库的实现原理是启动另外一个进程，启动 ffmpeg 并传递相应的处理参数，并根据进程输出获取处理进度

为了方便使用，实现了两个帮助类来方便的获取进程的输出，分别是 ProcessExecutor 和 CommandRunner，前者更为灵活，可以通过事件添加自己的额外事件订阅处理，后者为简化版，主要是只获取输出的场景，两者的实现原理大体是一样的，启动一个 Process，并监听其输出事件获取输出

`ProcessExecutor`

使用示例，这个示例是获取保存 nuget 包的路径的一个示例：

using var executor = new ProcessExecutor("dotnet", "nuget locals global-packages -l");

var folder = string.Empty;

executor.OnOutputDataReceived += (sender, str) =>

{

    if(str is null)

        return;

    Console.WriteLine(str);

    if(str.StartsWith("global-packages:"))

    {

        folder = str.Substring("global-packages:".Length).Trim();

    }

};

executor.Execute();

Console.WriteLine(folder);

ProcessExecutor 实现代码如下：

public class ProcessExecutor : IDisposable

{

    public event EventHandler<int> OnExited;

    public event EventHandler<string> OnOutputDataReceived;

    public event EventHandler<string> OnErrorDataReceived;

    protected readonly Process _process;

    protected bool _started;

    public ProcessExecutor(string exePath) : this(new ProcessStartInfo(exePath))

    {

    }

    public ProcessExecutor(string exePath, string arguments) : this(new ProcessStartInfo(exePath, arguments))

    {

    }

    public ProcessExecutor(ProcessStartInfo startInfo)

    {

        _process = new Process()

        {

            StartInfo = startInfo,

            EnableRaisingEvents = true,

        };

        _process.StartInfo.UseShellExecute = false;

        _process.StartInfo.CreateNoWindow = true;

        _process.StartInfo.RedirectStandardOutput = true;

        _process.StartInfo.RedirectStandardInput = true;

        _process.StartInfo.RedirectStandardError = true;

    }

    protected virtual void InitializeEvents()

    {

        _process.OutputDataReceived += (sender, args) =>

        {

            if (args.Data != null)

            {

                OnOutputDataReceived?.Invoke(sender, args.Data);

            }

        };

        _process.ErrorDataReceived += (sender, args) =>

        {

            if (args.Data != null)

            {

                OnErrorDataReceived?.Invoke(sender, args.Data);

            }

        };

        _process.Exited += (sender, args) =>

        {

            if (sender is Process process)

            {

                OnExited?.Invoke(sender, process.ExitCode);

            }

            else

            {

                OnExited?.Invoke(sender, _process.ExitCode);

            }

        };

    }

    protected virtual void Start()

    {

        if (_started)

        {

            return;

        }

        _started = true;

        _process.Start();

        _process.BeginOutputReadLine();

        _process.BeginErrorReadLine();

        _process.WaitForExit();

    }

    public async virtual Task SendInput(string input)

    {

        try

        {

            await _process.StandardInput.WriteAsync(input!);

        }

        catch (Exception e)

        {

            OnErrorDataReceived?.Invoke(_process, e.ToString());

        }

    }

    public virtual int Execute()

    {

        InitializeEvents();

        Start();

        return _process.ExitCode;

    }

    public virtual async Task<int> ExecuteAsync()

    {

        InitializeEvents();

        return await Task.Run(() =>

        {

            Start();

            return _process.ExitCode;

        }).ConfigureAwait(false);

    }

    public virtual void Dispose()

    {

        _process.Dispose();

        OnExited = null;

        OnOutputDataReceived = null;

        OnErrorDataReceived = null;

    }

}

`CommandExecutor`

上面的这种方式比较灵活但有些繁琐，于是有了下面这个版本

使用示例：

[Fact]

public void HostNameTest()

{

    if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))

    {

        return;

    }

    var result = CommandRunner.ExecuteAndCapture("hostname");

    var hostName = Dns.GetHostName();

    Assert.Equal(hostName, result.StandardOut.TrimEnd());

    Assert.Equal(0, result.ExitCode);

}

实现源码：

public static class CommandRunner

{

    public static int Execute(string commandPath, string arguments = null, string workingDirectory = null)

    {

        using var process = new Process()

        {

            StartInfo = new ProcessStartInfo(commandPath, arguments ?? string.Empty)

            {

                UseShellExecute = false,

                CreateNoWindow = true,

                WorkingDirectory = workingDirectory ?? Environment.CurrentDirectory

            }

        };

        process.Start();

        process.WaitForExit();

        return process.ExitCode;

    }

    public static CommandResult ExecuteAndCapture(string commandPath, string arguments = null, string workingDirectory = null)

    {

        using var process = new Process()

        {

            StartInfo = new ProcessStartInfo(commandPath, arguments ?? string.Empty)

            {

                UseShellExecute = false,

                CreateNoWindow = true,

                RedirectStandardOutput = true,

                RedirectStandardError = true,

                WorkingDirectory = workingDirectory ?? Environment.CurrentDirectory

            }

        };

        process.Start();

        var standardOut = process.StandardOutput.ReadToEnd();

        var standardError = process.StandardError.ReadToEnd();

        process.WaitForExit();

        return new CommandResult(process.ExitCode, standardOut, standardError);

    }

}

public sealed class CommandResult

{

    public CommandResult(int exitCode, string standardOut, string standardError)

    {

        ExitCode = exitCode;

        StandardOut = standardOut;

        StandardError = standardError;

    }

    public string StandardOut { get; }

    public string StandardError { get; }

    public int ExitCode { get; }

}

如果只要执行命令获取是否执行成功则使用 CommandRunner.Execute 即可，只获取输出和是否成功可以用 CommandRunner.ExecuteAndCapture 方法，如果想要进一步的添加事件订阅则使用 ProcessExecutor

巴特西

使用 C# 捕获进程输出

使用 C# 捕获进程输出

Intro

`ProcessExecutor`

`CommandExecutor`

More

Reference

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