管道问题

[ink8852]

新手，还请大家多关照
下面是一个匿名管道的例子，看了以后有几个问题：
1.关于DuplicateHandle函数。
这里为什么要创建一个副本，对于DuplicateHandle函数的用法还是不甚明了，还请大侠指教！
2.关于STD_INPUT_HANDLE,STD_OUTPUT_HANDLE。

#include "stdafx.h"
#include "windows.h"
#include "winbase.h"
#include "iostream.h"

int main(int argc, char* argv[])
{
HANDLE hProcess;
HANDLE hwrite;
HANDLE hread;

int i;
BOOL bTest;
DWORD dwWritten;

SECURITY_ATTRIBUTES sa;
STARTUPINFO sui; //子进程窗口属性结构
PROCESS_INFORMATION pi; //子进程信息

sa.bInheritHandle = TRUE;
sa.lpSecurityDescriptor = NULL;
sa.nLength = sizeof(SECURITY_ATTRIBUTES);

bTest = CreatePipe(&hread, &hwrite, &sa, 0);
if(!bTest)
{
cout<<"create pipe error"<<endl;
return -1;
}
bTest=DuplicateHandle(GetCurrentProcess(),
hwrite, GetCurrentProcess(),
NULL,0,FALSE,DUPLICATE_SAME_ACCESS);

if(!bTest){
cout<<"Dup Handle failed!"<<endl;

CloseHandle(hread);
CloseHandle(hwrite);
return -1;
}
memset(&sui,0, sizeof(STARTUPINFO));
sui.cb = sizeof(STARTUPINFO);
sui.dwFlags = STARTF_USESTDHANDLES;
sui.hStdInput = hread;
sui.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
sui.hStdError = GetStdHandle(STD_ERROR_HANDLE);

bTest = CreateProcess(NULL, "child.exe",NULL,NULL,TRUE,NULL,NULL,
NULL,&sui, &pi);
if(!bTest)
{
cout<<"create process failed"<<endl;
CloseHandle(hwrite);
CloseHandle(hread);
return -1;
}
else
{
hProcess = pi.hProcess;
CloseHandle(pi.hThread);
i = 100;
while(1)
{
bTest = WriteFile(hwrite, &i, sizeof (int),&dwWritten, NULL);
if(!bTest)
{
cout<<GetLastError()<<endl;
return -1;
}
Sleep(1000);
}
}
return 0;
}

[ink8852]

还没写完，不小心发出去了，继续
STD_INPUT_HANDLE是一个标准输入句柄，是每个进程有一个，还是windows里面只有一个？

[ink8852]

给分了

[ink8852]

songfen

[synchronization]

jiefen

[9731boy]

http://www.codeproject.com/internet/canonpipe.asp