File Permissions
 

I have file in my home directory.
I want other users on this system to be able to read from this file and write to this file.
But I don't want anyone to be able to delete this file.
How can I do this?

I guess what you want is not really possible. If you give write permission to a file, the person also has the right to delete it.

well This is possible, This happens the case with /tmp directory.
The non-owner user will not be able to delete it even if it has got 777 permission.

check the permission on /tmp directory. If am not sure wether you will be able to achieve what you exactly want but this is possible

Thats basically is sticy bit on /tmp i.e the last t in the permissions.

Explore over it.

It is possible, with the use of sticky bit. If you set it on a directory, then files inside that directory can only be renamed or removed by the owner of that directory, even if other users have write permissions to the files there.

That should do it. If you'll look at the permissions of a directory where sticky bit is set, you'll notice there are "t" letters where the usual "x" (execute) letters usually are. See

for an example

Allowing other users to access your home directory isn't a good idea. Put a copy of the file in /tmp/ or a publicly accessible directory which has the sticky bit set. In order to access this file, they would need rx permissions on the parent directory.

If this file is on an ext2 or ext3 filesystem, then you could use chattr +u.

This would make the file undeletable.