Linux file/directory permission question
 

Hi:

I read many documentation out there, many seems to be incorrect.
For example this one: http://www.zzee.com/solutions/linux-...k_9_1077830297

It says if I have write permission on directory, I will be able to add, rename, and delete files in the directory. The truth is not. I tested, it really need the execute permission, too, to be able to add, rename, and delete. So many information out there are wrong, this one, too: https://help.ubuntu.com/community/FilePermissions

Another weird thing is, if I have all read, write, execute permission to this directory. Even the files inside only has read permission, I can still edit them no problem. I used vim to edit, and to :w! to save them, and it works. Why is that?

Thanks.

Please give a specific example? No one here knows what you're seeing/doing,
so it's hard to say why what is going on.

You're working as root?

What cpthk is saying is true, really. What it says is to cd into the directory you have to have execute permission, but to change/create/remove files from the directory you have to have write permission.
If you have write permission and try to change/create/remove files from the directory without also having execute permission, you can't do it.
---
As far as having read permission only on the file and using vim and :w!, it forces a write. You don't have to use :w! if you have write permission.
When using vim in this situation and editing a file, it will say at the bottom:
When you try to write with :w, it will give the message:
Then you override it with :w!
That's all you're doing, is overriding it.

Look here:
http://www.tuxfiles.org/linuxhelp/filepermissions.html

I already gave example, I gave the website showing I only need write permission to add, rename, delete. But the truth is not.

No, I am not running as root.

But isn't file system suppose to enforce file security? If I can easily do override, then any virus or spyware could do it too. So you were saying vim ignore the file permission? What is the condition vim could override the permission? I suppose vim shouldn't override the permission in the case that those files really need to be protected.

You're right that you need execute permission on a directory to be able to do anything in it.

joeBuffer is incorrect, w! will not force a write on a read only file. If you try it, it will give you an error message

The result of w! on a readonly file abc.txt

My vim will do it fine. And why not? I own the file. vim can chmod write permissions onto it, write to the file, and them chmod them off. Files owned by root... that's another story.

Well ... if there's no actual question, but just a complaint
about some web-tutorial this thread is going to GENERAL.



Cheers,
Tink

OK, in my case it's elvis (on Slackware 10.1; vi is symlinked to it), not vim. I always forget about the difference :doh:

The result of :w in vim
and the result of :w! in vim
So there might be a difference between the implementations of vim in different distros or between versions of vim

And the permissions:

I have file permission:
In my case, vim still allow me to override and write to file. If I do:
I do:

I don't know the details, but this is what I've assumed happens.
W10: Warning: Changing a readonly file
E45: 'readonly' option is set (add ! to override)
"abc.txt" 1L, 4C written

It must be something they added in more recent versions...

You can modify vim's behaviour using the W flag in cpoptions

Keep in mind that the type of filesystem and the mount options(if on a separate partition) will affect your ability to read/write files also.