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Python, C: redirected stdout fires [Errno 9]
原标题:

I try to log all the output of a program written in Python and C. However, printing from Python causes IOError: [Errno 9] Bad file descriptor

Please, does anyone know what the problem is and how to fix it?

PS: It s on Windows XP, Python 2.6 and MinGW GCC

#include <windows.h>
#include <fcntl.h>
#include "Python.h"

int main()
{
    int fds[2];
    _pipe(fds, 1024, O_BINARY);
    _dup2(fds[1], 1);
    setvbuf(stdout, NULL, _IONBF, 0);

/*  alternative version: */
//  HANDLE hReadPipe, hWritePipe; 
//  int fd;
//  DWORD nr;
//  CreatePipe(&hReadPipe, &hWritePipe, NULL, 0);
//  fd = _open_osfhandle((intptr_t)hWritePipe, _O_BINARY);
//  _dup2(fd, 1);
//  setvbuf(stdout, NULL, _IONBF, 0);

    write(1, "write
", 6);
    printf("printf
");
    Py_Initialize();
    PyRun_SimpleString("print  print "); // this breaks
    Py_Finalize();

    char buffer[1024];
    fprintf(stderr, "buffer size: %d
", read(fds[0], buffer, 1024)); // should always be more than 0

/*  alternative version: */
//  CloseHandle(hWritePipe);
//  char buffer[1024];
//  ReadFile(hReadPipe, buffer, 1024, &nr, NULL);
//  fprintf(stderr, "buffer size: %d
", nr); // should always be more than 0
}

问题回答

I think it could be to do with different C runtimes. I know you can t pass file descriptors between different C runtimes - Python is built with MSVC (you will need to check which version) - so you could try to make MinGW build against the same C runtime - I think there is options to do this in MinGW like -lmsvcrt80 (or whichever is the appropriate versions) but for licensing reasons they can t distribute the libraries so you will have to find them on your system. Sorry I don t have any more details on that for now, but hopefully its a start for some googling.

A simpler way would be to just do it all in Python... just make a class which exposes a write and perhaps flush method and assign it to sys.stdout. Eg for a file you can just pass an open file object - it s probably straightfoward to do a similar thing for your pipe. Then just import it and sys and set sys.stdout in a PyRun_SimpleString.





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