如何从输出过程类中读取最后一行？

Question

I'm using Process class to start some process, it's calculating some data giving output at it's console and I need to read last line of process console. How it should be done? It's something with process.BeginOutputReadLine(); but I do not know how to use for read only LAST line.

Answer 1

string lastLine = null;
while (!process.StandardOutput.EndOfStream) 
{
    lastLine = process.StandardOutput.ReadLine();
}

//do what you want here with lastLine;

Answer 2

Here is the code that should do what you need:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication
{
    class Program
    {
        public static Process ShellStart(string aCmd, TextWriter aOutputWriter = null, TextWriter aErrorWriter = null)
        {
            var vProcess = new Process();
            var vStartInfo = vProcess.StartInfo;
            vStartInfo.FileName = Path.Combine(Environment.SystemDirectory, "CMD.EXE") ;
            var vCmd =  "/Q /C ";
            vStartInfo.Arguments = vCmd + "\"" + aCmd + "\"";
            vStartInfo.UseShellExecute = false;
            vStartInfo.CreateNoWindow = true;
            if (aOutputWriter != null)
            {
                vProcess.OutputDataReceived += (p, a) =>
                {
                    if (a.Data != null)
                    {
                        aOutputWriter.WriteLine(a.Data);
                    }
                };
                vStartInfo.RedirectStandardOutput = true;
                vStartInfo.RedirectStandardInput = true;
            }
            if (aErrorWriter != null)
            {
                vProcess.ErrorDataReceived += (p, a) =>
                {
                    if (a.Data != null)
                    {
                        aErrorWriter.WriteLine(a.Data);
                    }
                };
                vStartInfo.RedirectStandardError = true;
                vStartInfo.RedirectStandardInput = true;
            }
            if (!vProcess.Start()) return null;
            if (aOutputWriter != null || aErrorWriter != null)
                vProcess.Exited += (s, e) =>
                {
                    if (aOutputWriter != null) aOutputWriter.Flush();
                    if (aErrorWriter != null) aErrorWriter.Flush();
                };
            if (aOutputWriter != null) vProcess.BeginOutputReadLine();
            if (aErrorWriter != null) vProcess.BeginErrorReadLine();
            if (vStartInfo.RedirectStandardInput) vProcess.StandardInput.Close();
            return vProcess;
        }

        public static int ShellExec(string aCmd, TextWriter aOutputWriter = null, TextWriter aErrorWriter = null)
        {
            var vResult = -1;
            using (var vProcess = ShellStart(aCmd, aOutputWriter, aErrorWriter))
                if (vProcess != null)
                {
                    vProcess.WaitForExit();
                    vResult = vProcess.ExitCode;
                    vProcess.Close();
                }
            return vResult;
        }

        public static IEnumerable<String> SplitLines(string s)
        {
            string vLine;
            if (!String.IsNullOrEmpty(s))
                using (var vReader = new StringReader(s))
                    while ((vLine = vReader.ReadLine()) != null)
                    {
                        yield return vLine;
                    }
        }

        public static string ShellExecGetLastLine(string aCmd)
        {
            var vOutput = new StringBuilder();
            using (TextWriter vWriter = new StringWriter(vOutput))
            {
                ShellExec(aCmd, vWriter, null);
                return SplitLines(Convert.ToString(vOutput).Trim()).LastOrDefault();
            }
        }
        static void Main(string[] args)
        {
            Console.WriteLine(ShellExecGetLastLine("attrib"));
        }
    }
}

You can use ShellExecGetLastLine(command) where command is the path to your executable (along with the arguments, if required) to get the last line of the output.

In the example above, it calls attrib that outputs attributes of all files in the current directory, and returns the last line of output