[英]Cannot read from pipe in separate thread from suspended process
我正在嘗試使用處於掛起狀態的CreateProcess創建進程並從它的stdout讀取。 對於基礎我采用了MSDN代碼。 創建進程后,我將在進程上設置作業限制(尚未實現),然后我開始在STDOUT管道的單獨線程中讀取。 在線程啟動之前,我恢復暫停過程。 結果我從ReadFile調用中得不到任何東西,它只是停止並等待數據到達,即使進程完成。 這是代碼
#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_RdDup = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;
HANDLE g_hSavedStd_OUT_Wr = NULL;
HANDLE g_hInputFile = NULL;
DWORD WINAPI CreateChildProcess(LPVOID param);
void WriteToPipe(void);
DWORD WINAPI ReadFromPipe(LPVOID param);
void ErrorExit(PTSTR);
PROCESS_INFORMATION piProcInfo;
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"));
STARTUPINFO siStartInfo;
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;
//CreateThread(&saAttr,0, CreateChildProcess, &siStartInfo, 0, NULL);
CreateChildProcess(&siStartInfo);
ResumeThread(piProcInfo.hThread);
printf( "\n->Contents of child process STDOUT:\n\n", argv[1]);
//ReadFromPipe(NULL);
HANDLE thread = CreateThread(&saAttr,0, ReadFromPipe, &siStartInfo, 0, NULL);
WaitForSingleObject(thread, INFINITE);
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;
}
DWORD WINAPI CreateChildProcess(LPVOID param)
// Create a child process that uses the previously created pipes for STDIN and STDOUT.
{
TCHAR szCmdline[]=TEXT("C:\\GnuWin32\\bin\\ls.exe");
STARTUPINFO *siStartInfo = (STARTUPINFO*)param;
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.
// Create the child process.
bSuccess = CreateProcess(NULL,
szCmdline, // command line
NULL, // process security attributes
NULL, // primary thread security attributes
TRUE, // handles are inherited
CREATE_SUSPENDED | CREATE_SEPARATE_WOW_VDM | CREATE_NO_WINDOW, // creation flags
NULL, // use parent's environment
NULL, // use parent's current directory
siStartInfo, // STARTUPINFO pointer
&piProcInfo); // receives PROCESS_INFORMATION
//If resumethread is here - it works well
// 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);
}
return 0;
}
void WriteToPipe(void)
// 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;
for (;;)
{
bSuccess = ReadFile(g_hInputFile, chBuf, BUFSIZE, &dwRead, NULL);
if ( ! bSuccess || dwRead == 0 ) break;
bSuccess = WriteFile(g_hChildStd_IN_Wr, chBuf, dwRead, &dwWritten, NULL);
if ( ! bSuccess ) break;
}
// Close the pipe handle so the child process stops reading.
if ( ! CloseHandle(g_hChildStd_IN_Wr) )
ErrorExit(TEXT("StdInWr CloseHandle"));
}
DWORD WINAPI ReadFromPipe(LPVOID param)
// 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);
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;
}
return 0;
}
void ErrorExit(PTSTR lpszFunction)
// Format a readable error message, display a message box,
// and exit from the application.
{
LPVOID lpMsgBuf;
LPVOID lpDisplayBuf;
DWORD dw = GetLastError();
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dw,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR) &lpMsgBuf,
0, NULL );
lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT,
(lstrlen((LPCTSTR)lpMsgBuf)+lstrlen((LPCTSTR)lpszFunction)+40)*sizeof(TCHAR));
StringCchPrintf((LPTSTR)lpDisplayBuf,
LocalSize(lpDisplayBuf) / sizeof(TCHAR),
TEXT("%s failed with error %d: %s"),
lpszFunction, dw, lpMsgBuf);
MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK);
LocalFree(lpMsgBuf);
LocalFree(lpDisplayBuf);
ExitProcess(1);
}
如果我調用ResumeThread(piProcInfo.hThread); 就在CreateProcess函數之后 - 它運行良好。 但是我還是需要在單獨的函數中保持創建,然后調用ResumeThread之后的幾個函數。 所以,我想做什么來使程序在單獨的線程中獲得暫停進程的輸出。
始終檢查返回值。
你試圖在已經關閉的句柄上調用ResumeThread
。 如果你檢查了返回值,你會發現這個功能沒有成功,這會告訴你問題是什么。
從CreateChildProcess
刪除CloseHandle(piProcInfo.hThread)
,對ResumeThread
將起作用。
您可能還應該在創建子進程后關閉g_hChildStd_OUT_Wr
和g_hChildStd_IN_Rd
,以便您可以判斷子進程何時退出。
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