捕获控制台输出信息
启动DOS或者控制台程序，如何捕获运行时的输出信息？
比如，在dos窗口下，输入dir捕获文件夹列表信息？
有两篇文章已经说明了这个问题：
http://www.delphi3000.com/articles/article_2112.asp
http://www.delphi3000.com/articles/article_2298.asp
但是，他们都是在进程结束之后才获取输出信息
这样会有一些问题:
1）createPipe必须制定足够的size，否则，程序会死掉
2）如果程序createProcess成功，但是内部命令出错，会导致readfile时死掉
Microsoft Knowledge Base Article - Q190351
HOWTO: Spawn Console Processes with Redirected Standard Handles
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q190351
Microsoft Knowledge Base Article - Q150956
INFO: Redirection Issues on Windows 95 MS-DOS Applications
http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q150956
基本的思想是用CreateProcess启动一个控制台程序，把输入和输出用管道重定向，
允许调用进程访问控制台程序的输出信息
在进程依然运行中捕获输出时非常重要的，如果输出管道发生溢出，就会被阻止，
控制台程序就不能够将新的信息就覆盖到输出管道，并且导致程序停止，这种情况下
会锁死的：父进程等待子进程结束，而子进程等待父进程清空缓冲区
具体的实现如下：
代码const
ReadBuffer = 1048576; // 1 MB Buffer
var
Security : TSecurityAttributes;
ReadPipe,WritePipe : THandle;
start : TStartUpInfo;
ProcessInfo : TProcessInformation;
Buffer : Pchar;
TotalBytesRead,
BytesRead : DWORD;
Apprunning,n,
BytesLeftThisMessage,
TotalBytesAvail : integer;
begin
with Security do
begin
nlength := SizeOf(TSecurityAttributes);
binherithandle := true;
lpsecuritydescriptor := nil;
end;
if CreatePipe (ReadPipe, WritePipe, @Security, 0) then
begin
// Redirect In- and Output through STARTUPINFO structure
Buffer := AllocMem(ReadBuffer + 1);
FillChar(Start,Sizeof(Start),#0);
start.cb := SizeOf(start);
start.hStdOutput := WritePipe;
start.hStdInput := ReadPipe;
start.hStdError := WritePipe; //控制台错误信息也输出
start.dwFlags := STARTF_USESTDHANDLES + STARTF_USESHOWWINDOW;
start.wShowWindow := SW_HIDE;
// Create a Console Child Process with redirected input and output
if CreateProcess(nil ,PChar(DosApp),
@Security,@Security,
true ,CREATE_NO_WINDOW or NORMAL_PRIORITY_CLASS,
nil ,nil,
start ,ProcessInfo) then
begin
n:=0;
TotalBytesRead:=0;
repeat
// Increase counter to prevent an endless loop if the process is dead
Inc(n,1);
// wait for end of child process
Apprunning := WaitForSingleObject(ProcessInfo.hProcess,100);
Application.ProcessMessages;
// it is important to read from time to time the output information
// so that the pipe is not blocked by an overflow. New information
// can be written from the console app to the pipe only if there is
// enough buffer space.
if not PeekNamedPipe(ReadPipe ,@Buffer[TotalBytesRead],
ReadBuffer ,@BytesRead,
@TotalBytesAvail,@BytesLeftThisMessage) then break
else if BytesRead > 0 then
ReadFile(ReadPipe,Buffer[TotalBytesRead],BytesRead,BytesRead,nil);
TotalBytesRead:=TotalBytesRead+BytesRead;
until (Apprunning <> WAIT_TIMEOUT) or (n > 150);
Buffer[TotalBytesRead]:= #0;
OemToChar(Buffer,Buffer);
AMemo.Text := AMemo.text + StrPas(Buffer);
end;
FreeMem(Buffer);
CloseHandle(ProcessInfo.hProcess);
CloseHandle(ProcessInfo.hThread);
CloseHandle(ReadPipe);
CloseHandle(WritePipe);
end;
end;
