CGI File Upload

Bill Seitz fluxent at yahoo.com
Wed Dec 6 19:27:38 CET 2000


In article <90j10o$5p5$1 at nnrp1.deja.com>,
  Bill Seitz <fluxent at yahoo.com> wrote:
> In article <8u7fn7$jpf$1 at la-mail4.digilink.net>,
>   "Pete Shinners" <pete at visionart.com> wrote:
> > "Simon Faulkner" <news at titanic.co.uk> wrote
> > > I would like users to be able to upload .jpeg files via a web page
> > > <input type=file>
> > >
> > > What python code do I need to be able to save the file to a
> directory
> > > on the hard disk?
> >
> > i have some code that does this.. you'll probably want to clean
> > it to suit your own purposes, but here it is. at some point i
> > wanted to add PIL support to resize the images to a certain
> > resolution and convert them to be JPG, but that day hasn't come
> > yet... heh. note it also allows the user to save a comment as a
> > .TXT file. anyways, you can use it as a start for whatever you want
>
> Hmm, this works for me with text data (though the file length is
> slightly different: maybe line-end changes from Win to *nix?). With
> binary it's totally off. Uploading a JPEG I consistently only get 109
> bytes written to the file system. With GIFs I consistently get ~500
> bytes (but not always exactly the same number). With an MsWord file I
> get a bigger file written, but still not the whole thing (60kb out of
> 75kb).
>
> What do I do next?

Some recommendations were made by Barry Pederson
(bpederson at geocities.com). I didn't need them since setting the mode
was sufficient, but wanted to share them anyway, since others might
find them necessary/helpful...
--------

I was recently working on a CGI that did file uploads under
Win32/Apache, and found these 3 things needed adjusting for it to work
properly:

1. Make sure you use a fixed version of the cgi.py module.  The
the version in 2.0 or earlier reads the entire file upload
into memory, which is impractical in the case of multi-megabyte
uploads.  It's supposed to be fixed in Python 2.1, but
you can fix the 2.0 or earlier version yourself by commenting
out the 3 or so lines that call "self.lines.append()"

2. If on Win32, be sure to either arrange to run python with the
"-u" parameter, or with the PYTHONUNBUFFERED environment variable
set to 1.  Otherwise the uploaded files will be truncated if
characters such as Ctrl-Z appear in them.

This can be done in the Apache config with the SetEnv directive:

     SetEnv PYTHONUNBUFFERED 1

right after the ScriptAlias directive for example.

3. In addition to the fix listed above, you also will need a tweaked
version of rfc822.py (which is called by cgi.py), that puts a
try/except wrapper around the one call to tell() that doesn't
already have one.  It's been submitted as a bug to the Python guys,
and Guido says he's made my suggested fix, so it should also be in
Python 2.1.


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