UNIX for Dummies Questions & Answers

As I understand the file permissions in UNIX is basically

Owner, group, others

Lets assume scott user who's primary group is dev creates a file called test.dat and then grants some privileges on that file...

Code:

scott@unix-host> echo "this is a test" > test.dat
scott@unix-host> chmod 640 test.dat
scott@unix-host> ls -l test.dat

-rw-r-----   1 scott  dev   960 Apr  1  2011 test.dat

Now, let's assume user Tom who's primary group is also dev logs in and tries to delete the test.dat file created by scott..

Code:

tom@unix-host> rm test.dat
test.dat: 640  mode ? (y/n) y

surprisingly, Tom was able to delete the file. I thought only scott user would be able to delete test.dat file as only the "owner" (as in owner,group,others) has "rw" privilege..I'm a bit confused as to how Tom was able to delete the file even though "Group" has only Read access...Could you help me understand this?

Thanks for your time...


Thanks

as tom user, after answering yes to the remove command,
what output is given by the following command :

Code:

echo $?
ls -l test.dat
alias
ls -l $(type rm | awk '{print $NF}')
id

?

As odd as it seems this is expected behavior. The person's right to delete the file comes from the containing folder, not the file.

To avoid that, you need to set the "sticky" bit on the folder. That should make it so only the owner can delete the file.

Code:

chmod +t /path/to/set

May I suggest my tutorial on file permissions

Thanks to all for your time & input...Special thanks to Paberdo for the excellent tutorial material...

Thanks again