Windows Child Process의 STDOUT 출력을 받아오자. 실전 임베디드 2016. 11. 17. 0:00

이게 유닉스/리눅스에서는 너무 쉬운데 윈도우에서는 조금 까다롭다.

 

게다가 MSDN에 있는 샘플 코드에는 버그가 숨어있기까지 하다.

이 샘플이 가장 잘 동작한다. 원 소스를 공개한 분께 감사.

 

원본 주소는 이곳 : http://stackoverflow.com/questions/14147138/capture-output-of-spawned-process-to-string

Capture Output of Spawned Process to string

Background: I'm working on a program that needs to be able to capture the stdout, stderr and return values of a program. Ideally, I ...

stackoverflow.com

 

#include <string>
#include <iostream>
#include <windows.h>
#include <stdio.h>
#pragma warning( disable : 4800 ) // stupid warning about bool
#define BUFSIZE 4096
HANDLE g_hChildStd_OUT_Rd = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;
HANDLE g_hChildStd_ERR_Rd = NULL;
HANDLE g_hChildStd_ERR_Wr = NULL;

PROCESS_INFORMATION CreateChildProcess(void);
void ReadFromPipe(PROCESS_INFORMATION);

int main(int argc, char *argv[]){
    SECURITY_ATTRIBUTES sa;
    printf("\n->Start of parent execution.\n");
    // Set the bInheritHandle flag so pipe handles are inherited.
    sa.nLength = sizeof(SECURITY_ATTRIBUTES);
    sa.bInheritHandle = TRUE;
    sa.lpSecurityDescriptor = NULL;
    // Create a pipe for the child process's STDERR.
    if ( ! CreatePipe(&g_hChildStd_ERR_Rd, &g_hChildStd_ERR_Wr, &sa, 0) ) {
        exit(1);
    }
    // Ensure the read handle to the pipe for STDERR is not inherited.
    if ( ! SetHandleInformation(g_hChildStd_ERR_Rd, HANDLE_FLAG_INHERIT, 0) ){
        exit(1);
    }
    // Create a pipe for the child process's STDOUT.
    if ( ! CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &sa, 0) ) {
        exit(1);
    }
    // Ensure the read handle to the pipe for STDOUT is not inherited
    if ( ! SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0) ){
        exit(1);
    }
    // Create the child process.
    PROCESS_INFORMATION piProcInfo = CreateChildProcess();

    // Read from pipe that is the standard output for child process.
    printf( "\n->Contents of child process STDOUT:\n\n", argv[1]);
    ReadFromPipe(piProcInfo);

    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;
}

// Create a child process that uses the previously created pipes
//  for STDERR and STDOUT.
PROCESS_INFORMATION CreateChildProcess(){
    // Set the text I want to run
    char szCmdline[]="test --log_level=all --report_level=detailed";
    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 STDERR and STDOUT handles for redirection.
    ZeroMemory( &siStartInfo, sizeof(STARTUPINFO) );
    siStartInfo.cb = sizeof(STARTUPINFO);
    siStartInfo.hStdError = g_hChildStd_ERR_Wr;
    siStartInfo.hStdOutput = g_hChildStd_OUT_Wr;
    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    // Create the child process.
    bSuccess = CreateProcess(NULL,
        szCmdline,     // 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
    CloseHandle(g_hChildStd_ERR_Wr);
    CloseHandle(g_hChildStd_OUT_Wr);
    // If an error occurs, exit the application.
    if ( ! bSuccess ) {
        exit(1);
    }
    return piProcInfo;
}

// 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.
void ReadFromPipe(PROCESS_INFORMATION piProcInfo) {
    DWORD dwRead;
    CHAR chBuf[BUFSIZE];
    bool bSuccess = FALSE;
    std::string out = "", err = "";
    for (;;) {
        bSuccess=ReadFile( g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
        if( ! bSuccess || dwRead == 0 ) break;

        std::string s(chBuf, dwRead);
        out += s;
    }
    dwRead = 0;
    for (;;) {
        bSuccess=ReadFile( g_hChildStd_ERR_Rd, chBuf, BUFSIZE, &dwRead, NULL);
        if( ! bSuccess || dwRead == 0 ) break;

        std::string s(chBuf, dwRead);
        err += s;

    }
    std::cout << "stdout:" << out << std::endl;
    std::cout << "stderr:" << err << std::endl;
}