[Python-Dev] large file support

[Sean Reifschneider]

On Mon, Jun 17, 2002 at 11:02:42PM -0400, Guido van Rossum wrote:
>> How about changing os.path.exists for posix to:
>> 
>>    def exists(path):
>>       return(os.access(path, os.F_OK))
>
>NO, NO, NOOOOOOO!
>
>access() does something different.  It checks permissions as they

F_OK checks to see if the file exists.  Am I misunderstanding something in
the following test:

   [2] guin:tmp# cd /tmp
   [2] guin:tmp# mkdir test
   [2] guin:tmp# chmod 700 test
   [2] guin:tmp# touch test/exists
   [2] guin:tmp# chmod 700 test/exists
   [2] guin:tmp# su -c '/tmp/showaccess /tmp/test/exists' jafo
   access: 0   exists: 0
   [2] guin:tmp# chmod 111 /tmp/test
   [2] guin:tmp# su -c '/tmp/showaccess /tmp/test/exists' jafo
   access: 1   exists: 1
   [2] guin:tmp# chmod 000 test/exists
   [2] guin:tmp# su -c '/tmp/showaccess /tmp/test/exists' jafo
   access: 1   exists: 1
   [2] guin:tmp# chmod 000 /tmp/test
   [2] guin:tmp# su -c '/tmp/showaccess /tmp/test/exists' jafo
   access: 0   exists: 0
   [2] guin:tmp# su -c '/tmp/showaccess /tmp/test/noexists' jafo
   access: 0   exists: 0
   [2] guin:tmp# chmod 777 /tmp/test
   [2] guin:tmp# su -c '/tmp/showaccess /tmp/test/noexists' jafo
   access: 0   exists: 0

The above is run as root, with the su doing the test as non-root.  The code
in showaccess simply does an os.access and then an os.path.exists and
displays the results:

   [2] guin:tmp# cat /tmp/showaccess 
   #!/usr/bin/env python2

   import os, sys

   print 'access: %d   exists: %d' % ( os.access(sys.argv[1], os.F_OK),
         os.path.exists(sys.argv[1]))

Sean
-- 
 /home is where your .heart is.  -- Sean Reifschneider, 1999
Sean Reifschneider, Inimitably Superfluous <jafo@tummy.com>
tummy.com - Linux Consulting since 1995. Qmail, KRUD, Firewalls, Python