C++ 使用管道从子进程进行I/O重定向-winapi
我正在使用一个提供api的应用程序,这样编写脚本就更容易了。基本上,当您编写有效输入时,它会输出一个答案。我想使用该输出发送更多输入,例如:C++ 使用管道从子进程进行I/O重定向-winapi,c++,windows,io,pipe,child-process,C++,Windows,Io,Pipe,Child Process,我正在使用一个提供api的应用程序,这样编写脚本就更容易了。基本上,当您编写有效输入时,它会输出一个答案。我想使用该输出发送更多输入,例如: Input: <nodes> Output: 1, 56, 23 Input <56> Output: "Apple" 要么我把它留在那里,在我读了一次之后,我将无法写入我的子进程,要么我删除它,然后ReadFromPipe陷入死锁 任何帮助都将不胜感激,谢谢 ReadFile(…,BUFSIZE)表示“等待程序写入BUFSIZE
Input: <nodes>
Output: 1, 56, 23
Input <56>
Output: "Apple"
要么我把它留在那里,在我读了一次之后,我将无法写入我的子进程,要么我删除它,然后ReadFromPipe陷入死锁
任何帮助都将不胜感激,谢谢 ReadFile(…,BUFSIZE)
表示“等待程序写入BUFSIZE
字节,或关闭其管道末端”。程序只写入少量字节,然后等待更多的输入,而您没有提供这些输入。如果关闭写入管道,它知道没有更多输入,并退出,此时您的ReadFile知道没有更多输入并返回。您需要找到一种方法,只读取管道中的字节数
这里的神奇之处在于,它告诉您程序输出了多少数据,从而告诉您可以在不阻塞的情况下读取多少数据。请注意,您必须每隔一段时间不断检查一次,以查看程序自上次检查以来是否写入了更多字节。“要从子进程读取数据,首先需要关闭用于写入数据的父进程的句柄,”不,您不需要,总有办法做到这一点。我做过一次,我只需要记住,如果我删除行“CloseHandle(g_hchildsd_IN_Wr)”,程序就会卡在ReadFromPipe中的行“bSuccess=ReadFile(g_hchildsd_OUT_Rd,chBuf,BUFSIZE,&dwRead,NULL);”。虽然我不确定为什么会这样,但它确实。。。有什么解决办法吗?是的,我就是这么想的!但出于某种原因,“result=PeekNamedPipe(g_hchildsd_OUT_Rd,chBuf,BUFSIZE,&dwRead,&dwAvailableBytes,&dwbytesleet);”总是成功,但无论是否有字节要读取,dwRead、dwAvailableBytes和dwbytesleet总是设置为0。我会更深入地研究它,也许我遗漏了什么……你可能在流程编写之前检查过。你必须时不时地检查一下。当然,我是笨蛋!非常感谢你的帮助,多亏了你,我才得以成功!记录在案,第一句话不太正确。管道是一种特殊情况;每次在管道的另一端完成写入操作时,ReadFile都将退出。(在这个特定场景中,这没有多大帮助,但在某些情况下,它会大大简化事情。)
#include <Windows.h>
#include <string>
using std::string;
HANDLE g_hChildStd_OUT_Rd = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;
HANDLE g_hChildStd_IN_Rd = NULL;
HANDLE g_hChildStd_IN_Wr = NULL;
#define BUFSIZE 4096
void WriteToPipe(string msg);
void ReadFromPipe(void);
int main()
{
/*
* CREATE PIPES
*/
SECURITY_ATTRIBUTES saAttr;
// Set the bInheritHandle flag so pipe handles are inherited.
saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
saAttr.bInheritHandle = TRUE;
saAttr.lpSecurityDescriptor = NULL;
// Create pipes for the child process's STDOUT and STDIN,
// ensures both handle are not inherited
CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &saAttr, 0);
SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0);
CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &saAttr, 0);
SetHandleInformation(g_hChildStd_IN_Wr, HANDLE_FLAG_INHERIT, 0);
/*
* CREATE CHILD PROCESS
*/
TCHAR szCmdline[]=TEXT("target.exe");
STARTUPINFO siStartInfo;
PROCESS_INFORMATION piProcInfo;
// Set up members of the PROCESS_INFORMATION structure.
ZeroMemory( &piProcInfo, sizeof(PROCESS_INFORMATION) );
// Set up members of the STARTUPINFO structure.
// This structure specifies the STDIN and STDOUT handles for redirection.
ZeroMemory( &siStartInfo, sizeof(STARTUPINFO) );
siStartInfo.cb = sizeof(STARTUPINFO);
siStartInfo.hStdError = g_hChildStd_OUT_Wr;
siStartInfo.hStdOutput = g_hChildStd_OUT_Wr;
siStartInfo.hStdInput = g_hChildStd_IN_Rd;
siStartInfo.dwFlags |= STARTF_USESTDHANDLES;
CreateProcess(NULL, szCmdline, NULL, NULL, TRUE, 0,
NULL, NULL, &siStartInfo, &piProcInfo);
// Close handles to the child process and its primary thread.
// Some applications might keep these handles to monitor the status
// of the child process, for example.
CloseHandle(g_hChildStd_OUT_Wr);
CloseHandle(g_hChildStd_IN_Rd);
CloseHandle(piProcInfo.hProcess);
CloseHandle(piProcInfo.hThread);
/*
* ACTUAL APPLICATION
*/
WriteToPipe("<nodes>\n");
// Need to close the handle before reading
CloseHandle(g_hChildStd_IN_Wr); // PROBLEM HERE
ReadFromPipe();
WriteToPipe("<56>\n"); // I can't, as I have released the handle already
system("pause");
return 0;
}
void WriteToPipe(string msg)
{
WriteFile(g_hChildStd_IN_Wr, msg.c_str(), msg.size(), NULL, NULL);
}
void ReadFromPipe(void)
{
DWORD dwRead, dwWritten;
CHAR chBuf[BUFSIZE];
BOOL bSuccess = FALSE;
HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
for (;;)
{
bSuccess = ReadFile(g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
if( ! bSuccess || dwRead == 0 ) break;
bSuccess = WriteFile(hParentStdOut, chBuf, dwRead, &dwWritten, NULL);
if (! bSuccess ) break;
}
}
CloseHandle(g_hChildStd_IN_Wr);