我希望Firebird备份工具gbak将其输出写入Delphi流(没有中间文件).有一个命令行参数可以写入stdout而不是文件.然后我在JEDI的JclSysUtils中使用Execute方法来启动gbak并处理该输出.
它看起来像这样：
procedure DoBackup;
var
LBackupAbortFlag: Boolean;
LBackupStream: TStringStream;
begin
LBackupAbortFlag := False;
LBackupStream := TStringStream.Create;
try
Execute('"C:\path to\gbak.exe" -b -t -v -user SYSDBA -pas "pw" <db> stdout',LBackupStream.WriteString,// Should process stdout (backup)
SomeMemo.Lines.Append,// Should process stderr (log)
True,// Backup is "raw"
False,// Log is not
@LBackupAbortFlag);
LBackupStream.SaveToFile('C:\path to\output.fbk');
finally
LBackupStream.Free;
end;
end;
问题是输出文件太小而无法包含实际备份.我仍然看到文件内容的元素.我尝试了不同的流类型,但这似乎没有什么区别.这可能会出错？
更新
需要明确的是：其他解决方案也是受欢迎的.最重要的是,我需要一些可靠的东西.这就是为什么我首先选择JEDI,而不是重新发明这样的事情.那么,如果它不会太复杂,那就太好了.
解决方法
当您希望合并stdout和stderr时,我的第一个答案是有效的.但是,如果您需要将这些分开,那么这种方法是没有用的.我现在可以通过仔细阅读您的问题和您的评论,看到您确实希望将两个输出流分开.
现在,扩展我的第一个答案以涵盖这一点并非完全直截了当.问题是那里的代码使用阻塞I / O.如果你需要维修两个管道,那就有明显的冲突. Windows中常用的解决方案是异步I / O,在Windows世界中称为重叠I / O.但是,异步I / O的实现要比阻塞I / O复杂得多.
所以,我将提出一种仍然使用阻塞I / O的替代方法.如果我们想要服务多个管道,并且我们想要使用阻塞I / O,那么显而易见的结论是每个管道需要一个线程.这很容易实现 – 比异步选项容易得多.我们可以使用几乎相同的代码,但将阻塞读取循环移动到线程中.我的例子,以这种方式重新工作,现在看起来像这样：
{$APPTYPE CONSOLE}
uses
SysUtils,Classes,Windows;
type
TProcessOutputPipe = class
private
Frd: THandle;
Fwr: THandle;
public
constructor Create;
destructor Destroy; override;
property rd: THandle read Frd;
property wr: THandle read Fwr;
procedure CloseWritePipe;
end;
constructor TProcessOutputPipe.Create;
const
PipeSecurityAttributes: TSecurityAttributes = (
nLength: SizeOf(TSecurityAttributes);
bInheritHandle: True
);
begin
inherited;
Win32Check(CreatePipe(Frd,Fwr,@PipeSecurityAttributes,0));
Win32Check(SetHandleInformation(Frd,HANDLE_FLAG_INHERIT,0));//don't inherit read handle of pipe
end;
destructor TProcessOutputPipe.Destroy;
begin
CloseHandle(Frd);
if Fwr<>0 then
CloseHandle(Fwr);
inherited;
end;
procedure TProcessOutputPipe.CloseWritePipe;
begin
CloseHandle(Fwr);
Fwr := 0;
end;
type
TReadPipeThread = class(TThread)
private
FPipeHandle: THandle;
FStream: TStream;
protected
procedure Execute; override;
public
constructor Create(PipeHandle: THandle; Stream: TStream);
end;
constructor TReadPipeThread.Create(PipeHandle: THandle; Stream: TStream);
begin
inherited Create(False);
FPipeHandle := PipeHandle;
FStream := Stream;
end;
procedure TReadPipeThread.Execute;
var
Buffer: array [0..4096-1] of Byte;
BytesRead: DWORD;
begin
while ReadFile(FPipeHandle,Buffer,SizeOf(Buffer),BytesRead,nil) and (BytesRead<>0) do begin
FStream.WriteBuffer(Buffer,BytesRead);
end;
end;
function ReadOutputFromExternalProcess(const ApplicationName,CommandLine: string; stdout,stderr: TStream): DWORD;
var
stdoutPipe,stderrPipe: TProcessOutputPipe;
stdoutThread,stderrThread: TReadPipeThread;
StartupInfo: TStartupInfo;
ProcessInfo: TProcessInformation;
lpApplicationName: PChar;
ModfiableCommandLine: string;
begin
if ApplicationName='' then
lpApplicationName := nil
else
lpApplicationName := PChar(ApplicationName);
ModfiableCommandLine := CommandLine;
UniqueString(ModfiableCommandLine);
stdoutPipe := nil;
stderrPipe := nil;
stdoutThread := nil;
stderrThread := nil;
try
stdoutPipe := TProcessOutputPipe.Create;
stderrPipe := TProcessOutputPipe.Create;
ZeroMemory(@StartupInfo,SizeOf(StartupInfo));
StartupInfo.cb := SizeOf(StartupInfo);
StartupInfo.dwFlags := STARTF_USESHOWWINDOW or STARTF_USESTDHANDLES;
StartupInfo.wShowWindow := SW_HIDE;
StartupInfo.hStdOutput := stdoutPipe.wr;
StartupInfo.hStdError := stderrPipe.wr;
Win32Check(CreateProcess(lpApplicationName,PChar(ModfiableCommandLine),nil,True,CREATE_NO_WINDOW or NORMAL_PRIORITY_CLASS,StartupInfo,ProcessInfo));
stdoutPipe.CloseWritePipe;//so that the process is able to terminate
stderrPipe.CloseWritePipe;//so that the process is able to terminate
stdoutThread := TReadPipeThread.Create(stdoutPipe.rd,stdout);
stderrThread := TReadPipeThread.Create(stderrPipe.rd,stderr);
stdoutThread.WaitFor;
stderrThread.WaitFor;
Win32Check(WaitForSingleObject(ProcessInfo.hProcess,INFINITE)=WAIT_OBJECT_0);
Win32Check(GetExitCodeProcess(ProcessInfo.hProcess,Result));
finally
stderrThread.Free;
stdoutThread.Free;
stderrPipe.Free;
stdoutPipe.Free;
end;
end;
procedure Test;
var
stdout,stderr: TFileStream;
ExitCode: DWORD;
begin
stdout := TFileStream.Create('C:\Desktop\stdout.txt',fmCreate);
try
stderr := TFileStream.Create('C:\Desktop\stderr.txt',fmCreate);
try
ExitCode := ReadOutputFromExternalProcess('','cmd /c dir /s C:\Windows\system32',stdout,stderr);
finally
stderr.Free;
end;
finally
stdout.Free;
end;
end;
begin
Test;
end.
如果您希望添加对取消的支持,那么您只需在用户取消时添加对TerminateProcess的调用.这将使一切停止,函数将返回您提供给TerminateProcess的退出代码.我现在犹豫为你建议一个取消框架,但我认为这个答案中的代码现在非常接近满足你的要求.