问题
I'm trying to do something that appears to be out of scope for the System.Diagnostics.Process object. Acceptable answers can propose a different approach as long as it uses .net 4.5/c#5.
My program is calling gdalwarp.exe to perform a long running processes on large tiff files. Galwarp.exe outputs in this format.
Creating output file that is 6014P x 4988L.
Processing input file [FileName].tiff.
Using band 4 of source image as alpha.
Using band 4 of destination image as alpha.
0...10...20...30...40...50...60...70...80...90...100 - done.
The last line streams in slowly to indicate progress. I would like to read that line whenever it changes so I can move a progress bar keeping the user informed.
First I attempted to read Process.StandardOutput but it delivers no data until the entire process is complete. Second I tried to call Process.BeginOutputReadLine() and connect the event Process.OutputDataReceived but it only fires when a line is complete.
Here is the call to Execute GDalWarp.exe.
public static void ResizeTiff(string SourceFile, string DestinationFile, float ResolutionWidth, float ResolutionHeight, Guid ProcessId)
{
var directory = GDalBin;
var exe = Path.Combine(directory, "gdalwarp.exe");
var args = " -ts " + ResolutionWidth + " " + ResolutionHeight + " -r cubic -co \"TFW=YES\" \"" + SourceFile + "\" \"" + DestinationFile + "\"";
ExecuteProcess(exe, args, null, directory, 0, null, true, true, 0);
}
Here is my working code in a static function that only reads the output after the process exits.
public static string ExecuteProcess(string FilePath, string Args, string Input, string WorkingDir, int WaitTime = 0, Dictionary<string, string> EnviroVariables = null, bool Trace = false, bool ThrowError = true, int ValidExitCode = 0)
{
var processInfo =
"FilePath: " + FilePath + "\n" +
(WaitTime > 0 ? "WaitTime: " + WaitTime.ToString() + " ms\n" : "") +
(!string.IsNullOrEmpty(Args) ? "Args: " + Args + "\n" : "") +
(!string.IsNullOrEmpty(Input) ? "Input: " + Input + "\n" : "") +
(!string.IsNullOrEmpty(WorkingDir) ? "WorkingDir: " + WorkingDir + "\n" : "") +
(EnviroVariables != null && EnviroVariables.Count > 0 ? "Environment Variables: " + string.Join(", ", EnviroVariables.Select(a => a.Key + "=" + a.Value)) + "\n" : "");
if(Trace)
Log.Debug("Running external process with the following parameters:\n" + processInfo);
var startInfo = (string.IsNullOrEmpty(Args))
? new ProcessStartInfo(FilePath)
: new ProcessStartInfo(FilePath, Args);
if (!string.IsNullOrEmpty(WorkingDir))
startInfo.WorkingDirectory = WorkingDir;
startInfo.UseShellExecute = false;
startInfo.RedirectStandardOutput = true;
startInfo.RedirectStandardError = true;
startInfo.CreateNoWindow = true;
if (!string.IsNullOrEmpty(Input))
startInfo.RedirectStandardInput = true;
if (EnviroVariables != null)
foreach (KeyValuePair<String, String> entry in EnviroVariables)
startInfo.EnvironmentVariables.Add(entry.Key, entry.Value);
var process = new Process();
process.StartInfo = startInfo;
if (process.Start())
{
if (Input != null && Input != "")
{
process.StandardInput.Write(Input);
process.StandardInput.Close();
}
var standardError = "";
var standardOutput = "";
int exitCode = 0;
var errorReadThread = new Thread(new ThreadStart(() => { standardError = process.StandardError.ReadToEnd(); }));
var outputReadTread = new Thread(new ThreadStart(() => { standardOutput = process.StandardOutput.ReadToEnd(); }));
errorReadThread.Start();
outputReadTread.Start();
var sw = Stopwatch.StartNew();
bool timedOut = false;
try
{
while (errorReadThread.IsAlive || outputReadTread.IsAlive)
{
Thread.Sleep(50);
if (WaitTime > 0 && sw.ElapsedMilliseconds > WaitTime)
{
if (errorReadThread.IsAlive) errorReadThread.Abort();
if (outputReadTread.IsAlive) outputReadTread.Abort();
timedOut = true;
break;
}
}
if (!process.HasExited)
process.Kill();
if (timedOut)
throw new TimeoutException("Timeout occurred during execution of an external process.\n" + processInfo + "Standard Output: " + standardOutput + "\nStandard Error: " + standardError);
exitCode = process.ExitCode;
}
finally
{
sw.Stop();
process.Close();
process.Dispose();
}
if (ThrowError && exitCode != ValidExitCode)
throw new Exception("An error was returned from the execution of an external process.\n" + processInfo + "Exit Code: " + exitCode + "\nStandard Output: " + standardOutput + "\nStandard Error: " + standardError);
if (Trace)
Log.Debug("Process Exited with the following values:\nExit Code: {0}\nStandard Output: {1}\nStandard Error: {2}", exitCode, standardOutput, standardError);
return standardOutput;
}
else return null;
}
Can anyone help me read this output in realtime?
回答1:
Here is a solution of your problem but a little bit tricky, because gdalwarp.exe is blocking standart output, you can redirect its output to a file and read changes on it. It was possible to use FileSystemWatcher to detect changes in file but it is not reliable enough sometimes. A simple polling method of file size changes is used below in the outputReadThread if OutputCallback is not null.
Here is a call to ExecuteProcess with callback to receive process output immediately.
public static void ResizeTiff(string SourceFile, string DestinationFile, float ResolutionWidth, float ResolutionHeight, Guid ProcessId)
{
var directory = GDalBin;
var exe = Path.Combine(directory, "gdalwarp.exe");
var args = " -ts " + ResolutionWidth + " " + ResolutionHeight + " -r cubic -co \"TFW=YES\" \"" + SourceFile + "\" \"" + DestinationFile + "\"";
float progress = 0;
Action<string, string> callback = delegate(string fullOutput, string newOutput)
{
float value;
if (float.TryParse(newOutput, out value))
progress = value;
else if (newOutput == ".")
progress += 2.5f;
else if (newOutput.StartsWith("100"))
progress = 100;
};
ExecuteProcess(exe, args, null, directory, 0, null, true, true, 0, callback);
}
Here is a function to call any process and receive the results as they happen.
public static string ExecuteProcess(string FilePath, string Args, string Input, string WorkingDir, int WaitTime = 0, Dictionary<string, string> EnviroVariables = null, bool Trace = false, bool ThrowError = true, int ValidExitCode = 0, Action<string, string> OutputChangedCallback = null)
{
var processInfo =
"FilePath: " + FilePath + "\n" +
(WaitTime > 0 ? "WaitTime: " + WaitTime.ToString() + " ms\n" : "") +
(!string.IsNullOrEmpty(Args) ? "Args: " + Args + "\n" : "") +
(!string.IsNullOrEmpty(Input) ? "Input: " + Input + "\n" : "") +
(!string.IsNullOrEmpty(WorkingDir) ? "WorkingDir: " + WorkingDir + "\n" : "") +
(EnviroVariables != null && EnviroVariables.Count > 0 ? "Environment Variables: " + string.Join(", ", EnviroVariables.Select(a => a.Key + "=" + a.Value)) + "\n" : "");
string outputFile = "";
if (OutputChangedCallback != null)
{
outputFile = Path.GetTempFileName();
Args = "/C \"\"" + FilePath + "\" " + Args + "\" >" + outputFile;
FilePath = "cmd.exe";
}
var startInfo = (string.IsNullOrEmpty(Args))
? new ProcessStartInfo(FilePath)
: new ProcessStartInfo(FilePath, Args);
if (!string.IsNullOrEmpty(WorkingDir))
startInfo.WorkingDirectory = WorkingDir;
startInfo.UseShellExecute = false;
startInfo.CreateNoWindow = true;
if (OutputChangedCallback == null)
{
startInfo.RedirectStandardOutput = true;
startInfo.RedirectStandardError = true;
}
else
{
startInfo.RedirectStandardOutput = false;
startInfo.RedirectStandardError = false;
}
if (!string.IsNullOrEmpty(Input))
startInfo.RedirectStandardInput = true;
if (EnviroVariables != null)
foreach (KeyValuePair<String, String> entry in EnviroVariables)
startInfo.EnvironmentVariables.Add(entry.Key, entry.Value);
var process = new Process();
process.StartInfo = startInfo;
if (process.Start())
{
if (Trace)
Log.Debug("Running external process with the following parameters:\n" + processInfo);
try
{
if (!string.IsNullOrEmpty(Input))
{
process.StandardInput.Write(Input);
process.StandardInput.Close();
}
var standardError = "";
var standardOutput = "";
int exitCode = 0;
Thread errorReadThread;
Thread outputReadThread;
if (OutputChangedCallback == null)
{
errorReadThread = new Thread(new ThreadStart(() => { standardError = process.StandardError.ReadToEnd(); }));
outputReadThread = new Thread(new ThreadStart(() => { standardOutput = process.StandardOutput.ReadToEnd(); }));
}
else
{
errorReadThread = new Thread(new ThreadStart(() => { }));
outputReadThread = new Thread(new ThreadStart(() =>
{
long len = 0;
while (!process.HasExited)
{
if (File.Exists(outputFile))
{
var info = new FileInfo(outputFile);
if (info.Length != len)
{
var content = new StreamReader(File.Open(outputFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)).ReadToEnd();
var newContent = content.Substring((int)len, (int)(info.Length - len));
len = info.Length;
OutputChangedCallback.Invoke(content, newContent);
}
}
Thread.Sleep(10);
}
}));
}
errorReadThread.Start();
outputReadThread.Start();
var sw = Stopwatch.StartNew();
bool timedOut = false;
try
{
while (errorReadThread.IsAlive || outputReadThread.IsAlive)
{
Thread.Sleep(50);
if (WaitTime > 0 && sw.ElapsedMilliseconds > WaitTime)
{
if (errorReadThread.IsAlive) errorReadThread.Abort();
if (outputReadThread.IsAlive) outputReadThread.Abort();
timedOut = true;
break;
}
}
if (!process.HasExited)
process.Kill();
if (timedOut)
throw new TimeoutException("Timeout occurred during execution of an external process.\n" + processInfo + "Standard Output: " + standardOutput + "\nStandard Error: " + standardError);
exitCode = process.ExitCode;
}
finally
{
sw.Stop();
process.Close();
process.Dispose();
}
if (ThrowError && exitCode != ValidExitCode)
throw new Exception("An error was returned from the execution of an external process.\n" + processInfo + "Exit Code: " + exitCode + "\nStandard Output: " + standardOutput + "\nStandard Error: " + standardError);
if (Trace)
Log.Debug("Process Exited with the following values:\nExit Code: {0}\nStandard Output: {1}\nStandard Error: {2}", exitCode, standardOutput, standardError);
return standardOutput;
}
finally
{
FileUtilities.AttemptToDeleteFiles(new string[] { outputFile });
}
}
else
throw new Exception("The process failed to start.\n" + processInfo);
}
来源：https://stackoverflow.com/questions/22991115/read-process-standardoutput-before-new-line-received