【发布时间】：2017-10-06 17:41:10
【问题描述】：
您好，我正在尝试为 cmd.exe 制作前端 GUI，以便将其扩大，但我卡住了。
我尝试设计这样的 API
char* Directory = WriteCommand("dir");
printf("- %s\n", Directory);
并且输出看起来与 cmd 窗口中的完全一样，除了我将它放在一个字符串中，所以它会是
DATE TIME FILESIZE FILENAME
etc etc etc
然后我可以发出
char* Up = WriteCommand ("cd ..");
它会给我上面的目录列表。所以我想要一个通过使用管道读写的终端控制。
我根据这个 MSDN 示例代码尝试了很多东西 - https://msdn.microsoft.com/en-us/library/ms682499.aspx
但我认为这段代码只适用于发出一个命令并读取一个响应，因为在此处描述的死锁之后 - https://blogs.msdn.microsoft.com/oldnewthing/20110707-00/?p=10223
我在这里看到了其他几个问题，比如这个有类似问题的问题 - How to read output from cmd.exe using CreateProcess() and CreatePipe() 但没有发布适合我的解决方案。
这是我的代码。
#include <windows.h>
#include <tchar.h>
#include <stdio.h>
#include <strsafe.h>
#define BUFSIZE 4096
HANDLE g_hChildStd_IN_Rd = NULL;
HANDLE g_hChildStd_IN_Wr = NULL;
HANDLE g_hChildStd_OUT_Rd = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;
HANDLE g_hInputFile = NULL;
void CreateChildProcess(void);
void WriteToPipe(char* Arg1);
void ReadFromPipe(void);
void ErrorExit(PTSTR);
int _tmain(int argc, TCHAR *argv[])
{
SECURITY_ATTRIBUTES saAttr;
printf("\n->Start of parent execution.\n");
// Set the bInheritHandle flag so pipe handles are inherited.
saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
saAttr.bInheritHandle = TRUE;
saAttr.lpSecurityDescriptor = NULL;
// Create a pipe for the child process's STDOUT.
if (!CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &saAttr, 0))
ErrorExit(TEXT("StdoutRd CreatePipe"));
// Ensure the read handle to the pipe for STDOUT is not inherited.
if (!SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0))
ErrorExit(TEXT("Stdout SetHandleInformation"));
// Create a pipe for the child process's STDIN.
if (!CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &saAttr, 0))
ErrorExit(TEXT("Stdin CreatePipe"));
// Ensure the write handle to the pipe for STDIN is not inherited.
if (!SetHandleInformation(g_hChildStd_IN_Wr, HANDLE_FLAG_INHERIT, 0))
ErrorExit(TEXT("Stdin SetHandleInformation"));
// Create the child process.
CreateChildProcess();
// Get a handle to an input file for the parent.
// This example assumes a plain text file and uses string output to verify data flow.
/*if (argc == 1)
ErrorExit(TEXT("Please specify an input file.\n"));
g_hInputFile = CreateFile(
argv[1],
GENERIC_READ,
0,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_READONLY,
NULL);
if (g_hInputFile == INVALID_HANDLE_VALUE)
ErrorExit(TEXT("CreateFile"));*/
// Write to the pipe that is the standard input for a child process.
// Data is written to the pipe's buffers, so it is not necessary to wait
// until the child process is running before writing data.
// Read from pipe that is the standard output for child process.
ReadFromPipe();
WriteToPipe("ipconfig");
// THIS IS WHERE DEADLOCK OCCURS, FROM HERE
// PROGRAM BECOMES UNRESPONSIVE - HOW TO FIX THIS?
ReadFromPipe();
printf("\n->End of parent execution.\n");
// The remaining open handles are cleaned up when this process terminates.
// To avoid resource leaks in a larger application, close handles explicitly.
return 0;
}
void CreateChildProcess()
// Create a child process that uses the previously created pipes for STDIN and STDOUT.
{
TCHAR szCmdline[] = TEXT("cmd.exe /k");
PROCESS_INFORMATION piProcInfo;
STARTUPINFO siStartInfo;
BOOL bSuccess = FALSE;
// 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;
// Create the child process.
bSuccess = CreateProcess(NULL,
"cmd.exe", // command line
NULL, // process security attributes
NULL, // primary thread security attributes
TRUE, // handles are inherited
0, // creation flags
NULL, // use parent's environment
NULL, // use parent's current directory
&siStartInfo, // STARTUPINFO pointer
&piProcInfo); // receives PROCESS_INFORMATION
// If an error occurs, exit the application.
if (!bSuccess)
ErrorExit(TEXT("CreateProcess"));
else
{
// 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(piProcInfo.hProcess);
CloseHandle(piProcInfo.hThread);
}
}
void WriteToPipe(char* Command)
// Read from a file and write its contents to the pipe for the child's STDIN.
// Stop when there is no more data.
{
DWORD dwRead, dwWritten;
CHAR chBuf[BUFSIZE];
BOOL bSuccess = FALSE;
bSuccess = WriteFile(g_hChildStd_IN_Wr, Command, strlen(Command), &dwWritten, NULL);
if (bSuccess == FALSE)
printf("write fail\n");
printf("written = %i\n", dwWritten);
//for (;;)
//{
//bSuccess = ReadFile(g_hInputFile, chBuf, BUFSIZE, &dwRead, NULL);
//if (!bSuccess || dwRead == 0) break;
//bSuccess = WriteFile(g_hChildStd_IN_Wr, Command, strlen(Command), &dwWritten, NULL);
//if (bSuccess == FALSE)
//printf("write fail\n");
//printf("written = %i\n", dwWritten);
//}
// Close the pipe handle so the child process stops reading.
//if (!CloseHandle(g_hChildStd_IN_Wr))
//ErrorExit(TEXT("StdInWr CloseHandle"));
}
void ReadFromPipe(void)
// Read output from the child process's pipe for STDOUT
// and write to the parent process's pipe for STDOUT.
// Stop when there is no more data.
{
DWORD dwRead, dwWritten;
CHAR chBuf[BUFSIZE];
BOOL bSuccess = FALSE;
HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
int i;
for (i = 0; i < 4; i++)
{
/*DWORD dwAvail = 0;
if (!PeekNamedPipe(g_hChildStd_OUT_Rd, NULL, 0, NULL, &dwAvail, NULL)) {
// error, the child process might have ended
break;
}
if (!dwAvail) {
// no data available in the pipe
break;
}*/
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;*/
chBuf[dwRead] = '\0';
printf("%i - %s\n", i, chBuf);
}
printf("done\n");
}
我发出初始的“cmd.exe”命令，它让我开始了命令提示符。我现在想发出“ipconfig”（或任何其他命令）来获取网络信息。程序死锁并变得无响应。我无法再读取子进程的输出。我怎样才能解决这个问题？感谢您的帮助。
【问题讨论】：
-
如果您为自己的程序创建异步管道句柄并且将使用管道进行异步工作 - 您永远不会遇到死锁
-
1) 你只需要通过
CreateNamedPipe（和FILE_FLAG_OVERLAPPED）+CreateFile创建一个管道对。您在代码中创建 两个 管道对。 2.) 通过BindIoCompletionCallback或CreateThreadpoolIo将您的管道端绑定到IOCP 3) 调用只需调用ReadFile，然后每次从竞争回调中再次调用ReadFile，当之前的ReadFile完成时没有错误。 4）很少，如果您需要在普通过程中处理读取结果，而不是在回调中，您可以创建光纤，在读取数据回调中 - 切换到光纤，并在处理数据后切换回 -
@RbMm：代码正在创建 2 个管道对，因为它正在重定向 STDIN 和 STDOUT。两者不能使用相同的管道。
-
@RemyLebeau - 你错了。我很多时候用 one 管道对编写代码。这是完美的工作。分配给 STDIN 和 STDOUT 的 same 管道句柄。我们可以在管道上进行读写操作
-
需要通过
CreateNamedPipe和PIPE_ACCESS_DUPLEX创建管道对 - 管道将是双向的；服务器和客户端进程都可以读取和写入管道。我说这不是理论上的，但很多时候在代码中实现它