[sf-perl] Bug in perl (or does -r not do what I think?)

Garth Webb garth.webb at gmail.com
Fri Jun 6 13:10:54 PDT 2008

Your OS says that root can read everything:

[garth at saba test]$ ls -l foo
-r-------- 1 someuser someuser 5 2008-06-06 13:09 foo
[garth at saba test]$ cat foo
cat: foo: Permission denied
[garth at saba test]$ su
[root at saba test]# cat foo
[root at saba test]#

On Fri, Jun 6, 2008 at 1:04 PM, Dan Boger <dan at peeron.com> wrote:

> I'm a little bit confused here, maybe one of you guys can spot what I'm
> missing.
> I have some files on an NFS filesystem, that is set to root_squash.  The
> file is owned by my network id (dboger), while I'm logged in locally as dan:
> dan at dbdb$ ls -l somefile.png
> -r-------- 1 dboger 3813 2008-06-05 16:46 somefile.png
> I'm trying to figure out if a file is readable, so I do something like:
> dan at dbdb$ perl -le 'print "lies" if -r shift' somefile.png
> dan at dbdb$
> That is correct - the file is owned by a different UID, and is set to 0400.
> Now, I try the same thing as root:
> dan at dbdb$ sudo perl -le 'print "lies" if -r shift' somefile.png
> lies
> dan at dbdb$ sudo file somefile.png
> couldn't open file
> somefile.png: regular file, no read permission
> Is perl just assuming that if I'm root I can always read the file, even
> though the permissions say that's wrong?
> What am I missing?
> Dan
> --
> Dan Boger
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