Hello,

I'm trying to write a simple Win32 app, which may run some Python
scripts. Since it is a Windows GUI app, I would like to redirect all
output (Python print, C printf, fprinf stderr, ...) to a text area
inside the app. In other words, I'm trying to log all the output from
the app (C, Python) to a window. So far, this works for C printf():

int fds[2];
_pipe(fds, 1024, O_TEXT);
_dup2(fds[1], 1);
...
and then I read from pipe's read-end and append the text to the text
area.

But when I try to run:
Py_Initialize();
PyRun_SimpleString("print 'abc'");
Py_Finalize();

I get an error:
IOError: [Errno 9] Bad file descriptor

What am I doing wrong? How to redirect standard IO, both for C and for
Python?
PS: Maybe I'm doind something wrong, but SetStdHandle() does not work
at all....

On Nov 15, 5:28 pm, Ecir Hana <ecir.h...@gmail.com> wrote:

Also, maybe this matters: it's on WinXP, Python 2.6 and MinGW GCC.

En Mon, 16 Nov 2009 14:17:52 -0300, Ecir Hana <ecir.h...@gmail.com>  
escribió:

This worked for me:

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

int main()
{
   HANDLE hReadPipe, hWritePipe;
   DWORD nr, nw;
   char buffer[100];

   CreatePipe(
     &hReadPipe,
     &hWritePipe,
     NULL,
     1024);
   SetStdHandle(STD_OUTPUT_HANDLE, hWritePipe);

   Py_Initialize();
   PyRun_SimpleString("print 'from Python'");
   Py_Finalize();

   puts("from C\n");

   CloseHandle(hWritePipe);
   ReadFile(hReadPipe, buffer, 19, &nr, NULL);
   CloseHandle(hReadPipe);
   WriteFile(GetStdHandle(STD_ERROR_HANDLE), buffer, nr, &nw, NULL);

I'm using Visual Studio 2008 Express Edition.

--
Gabriel Genellina

On Nov 16, 7:21 pm, "Gabriel Genellina" <gagsl-...@yahoo.com.ar>
wrote:

Hi,

thanks for the reply!

However, please, could you tell me how many bytes it read here:

ReadFile(hReadPipe, buffer, 19, &nr, NULL);

because for me, it has read 0. When I run your code, it prints from
both C and Python, but it prints straight to the console, not to the
buffer. Could you also please try to add:

WriteFile(GetStdHandle(STD_ERROR_HANDLE), "----\n", 5, &nw, NULL);

before:

WriteFile(GetStdHandle(STD_ERROR_HANDLE), buffer, nr, &nw, NULL);

Does it print "----" before "from Python" and "from C" for you?
Because for me it comes afterwards (as nr is 0)...

En Mon, 16 Nov 2009 18:04:21 -0300, Ecir Hana <ecir.h...@gmail.com>  
escribió:

Sorry, my earlier code was not working as I expected; I wrongly assumed  
the output was being redirected but that was not the case.
The version below ("set paranoid mode on") does redirect printf(),  
fwrite(stdout,...), write(1,...), WriteFile(consolehandle,...), all those  
calls in C, but fails in Python with IOError: [Errno 9] Bad file  
descriptor.
I'm unable to figure out *where* it fails just by reading the Python  
source; one should set a breakpoint in python26.dll to see what actually  
happens.

The code below now reads from the pipe everything that has been written --  
except from Python :(

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

int error(char* lpszText)
{
     LPVOID lpMsgBuf;
     DWORD lasterror = GetLastError();

     FormatMessage(
         FORMAT_MESSAGE_ALLOCATE_BUFFER |
         FORMAT_MESSAGE_FROM_SYSTEM |
         FORMAT_MESSAGE_IGNORE_INSERTS,
         NULL,
         lasterror,
         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
         (LPTSTR) &lpMsgBuf,
         0, NULL );
     fprintf(stderr,
         "%s: error %d: %s",
         lpszText, lasterror, lpMsgBuf);
     LocalFree(lpMsgBuf);
     return 1;

int main()
{
   HANDLE hReadPipe, hWritePipe;
   DWORD nr, nw;
   char buffer[100];
   int fd, i;
   BOOL bResult;

   if (!CreatePipe(
     &hReadPipe,
     &hWritePipe,
     NULL,
         0))
     return error("cannot create pipe");
   if (!SetStdHandle(STD_OUTPUT_HANDLE, hWritePipe))
     return error("SetStdHandle");

   // this was missing in previous version
   fd = _open_osfhandle((intptr_t)hWritePipe, _O_TEXT);
   if (fd==-1) return error("_open_osfhandle");
   if (_dup2(fd, 1)!=0) return error("dup2");

   if (!WriteFile(hWritePipe, "WriteFile(pipe)\n", 16, &nr, NULL)) return  
error("WriteFile(pipe)");
   if (!WriteFile(GetStdHandle(STD_OUTPUT_HANDLE), "WriteFile(stdout)\n",  
18, &nr, NULL)) return error("WriteFile(stdout)");
   fputs("fputs from C\n", stdout);
   if (fwrite("fwrite from C\n", 1, 14, stdout)!=14) return  
error("fwrite!=14");
   if (write(1, "write from C\n", 13)<0) return error("write");
   fflush(stdout);

   fprintf(stderr, "before Python\n");
   Py_Initialize();
   PyRun_SimpleString("import sys;sys.stdout.write('from Python\\n')\n");
   Py_Finalize();

   fprintf(stderr, "before flush 2\n");
   fflush(stdout);

   fprintf(stderr, "before close pipe w\n");
   if (!CloseHandle(hWritePipe)) return error("CloseHandle(hWritePipe)");
   fprintf(stderr, "before close STDOUT Handle\n");
   if (!CloseHandle(GetStdHandle(STD_OUTPUT_HANDLE))) return  
error("CloseHandle(STDOUT)");
   fprintf(stderr, "before read pipe\n");
   // read one char at a time...
   for (i = 0; i<sizeof(buffer); i++) {
     bResult = ReadFile(hReadPipe, &buffer[i], 1, &nr, NULL);
     if ((!bResult) || (nr==0))
         break;
   }
   buffer[i]='\0';
   fprintf(stderr, "before close pipe r\n");
   if (!CloseHandle(hReadPipe)) return error("CloseHandle(hReadPipe)");
   fprintf(stderr, "==========\nnread=%d\n%s\n", i, buffer);
   return 0;

</code>

--
Gabriel Genellina

On Nov 17, 6:51 am, "Gabriel Genellina" <gagsl-...@yahoo.com.ar>
wrote:

Thanks a lot for the fine code! So far I don't know why it fails to
print from Python - I'll post here any news I get...