Re: stderr, stdout, and errno 24

[Lawrence D'Oliveiro]

In article <[EMAIL PROTECTED]>,
 "Wesley Henwood" <[EMAIL PROTECTED]> wrote:

>I've checked and double checked my code and I am closing all files
>explicitly after opening them.

If you're running your program under Linux, a very easy way to confirm 
this is to look in the directory

/proc//fd

where  is the PID of your running program. In here you will see a 
symlink to every file your program has open, the name of the link being 
the file descriptor number.

To make it easier to watch, you may want to stick in a sleep of a few 
seconds in-between iterations of the code that executes the Python 
script.

If you see the entries piling up in this directory, that will confirm 
that you're not closing those files.
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Re: stderr, stdout, and errno 24

[alisonken1]

Wesley Henwood wrote:
> I've checked and double checked my code and I am closing all files
> explicitly after opening them.  The only possibliy I can think of is
> Python opening files each time I run a script, or each time imput to
> stderr or stdout is redirected.
>


The problem >I think< is that stout and stderr are not shared with each
invocation.

Since you're calling a python interpreter, the stdout/stderr from the
C++ program is not inherited - so now everytime you call the python
script, it's creating a new process.

With each new process, you're creating a new stdout/stderr handle, and
if you're calling outside of C++ relatively quickly (say more than 100
times a minute), then the old stdout/stderr handles have not had a
chance to be garbage collected - hence, you get too many files open
errors.

The workaround would possibly be to create a Python thread or create a
stdout fifo and a stderr fifo and have your script redirect these
outputs through the fifo buffers that you're C++ code can listen to.

Not sure how to do either one in MS environments, so you'll have to ask
someone else how to work with them.

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Re: stderr, stdout, and errno 24

[Wesley Henwood]

I've checked and double checked my code and I am closing all files
explicitly after opening them.  The only possibliy I can think of is
Python opening files each time I run a script, or each time imput to
stderr or stdout is redirected.

Here's a link that is perhaps related to my
problem:

Here is a thread in this group, see post by
alisonken1:

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Re: stderr, stdout, and errno 24

[Jim Segrave]

In article <[EMAIL PROTECTED]>,
Wesley Henwood <[EMAIL PROTECTED]> wrote:
>To capture output from python scripts run from a C++ app I've added the
>following code at the beggening of the C++ app:
>
>PyRun_SimpleString("import grabber");
>PyRun_SimpleString("import sys");
>PyRun_SimpleString("class a:\n\tdef
>write(self,s):\n\t\tograbber.grab(s)\n");
>PyRun_SimpleString("import sys\nsys.stderr=a()\nsys.stdout=a()");
>
>Its hard to read that way, here's what it expands to:
>import grabber
>import sys
>class a:
>def write(self, s)
>grabber.grab(s)
>
>grabber is a C++ extension, the grab function prints displays the
>captured text in a Windows app.  After running about 450+ scripts in a
>row, I get "IOError Errno 24 Too many open files."
>
>I've searched this group and the net and determined that stderr and
>stdout may open files, is that correct?  If so would each running of a
>script be opening new files related to stderr and stdout and not
>closing them?  I'm just guessing.

I'm guessing, but it sounds like perhaps you're creating an object which has
an open file handle for output for each script that's run. When the
script finishes, if that object still exists, it will keep a file
handle open and eventually you'll hit the system limit on open file
handles for one process. 

It's also possible that your C++ app is the one which is failing to
close file handles created for running the scripts - there's no easy
way to tell from the information posted. 

You need to examine carefully what happens to any stdin/stdout/stderr
files which are created to execute scripts and ensure that they are
all properly closed (or, in the case of Python, if you don't
explicitly close them, that any references to the files cease to exist
after the script runs). I'd personally recommend explicit closing
here.




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Jim Segrave   ([EMAIL PROTECTED])

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Re: stderr, stdout, and errno 24

[Dave Hansen]

On 12 Jul 2006 18:09:42 -0700 in comp.lang.python, "Wesley Henwood"
<[EMAIL PROTECTED]> wrote:

>To capture output from python scripts run from a C++ app I've added the
>following code at the beggening of the C++ app:
>
>PyRun_SimpleString("import grabber");
>PyRun_SimpleString("import sys");
>PyRun_SimpleString("class a:\n\tdef
>write(self,s):\n\t\tograbber.grab(s)\n");
>PyRun_SimpleString("import sys\nsys.stderr=a()\nsys.stdout=a()");
>
>Its hard to read that way, here's what it expands to:
>import grabber
>import sys
>class a:
>def write(self, s)
>grabber.grab(s)

Actually, that last line will more like
>ograbber.grab(s)

At least, if what you posted above is accurate...

It's not the question you asked, but if you want to make that easier
to read, you can do something like

   PyRun_SimpleString("import grabber");
   PyRun_SimpleString("import sys");

   PyRun_SimpleString("class a:\n"
  "   def write(self,s):\n"
  "  grabber.grab(s)\n");

   PyRun_SimpleString("import sys\n"
  "sys.stderr=a()\n"
  "sys.stdout=a()\n");


C++, like Python, will concatenate strings seperated only by
whitespace.

Regards,
-=Dave

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