Files permissions

The files permissions under Haiku let you choose if a file or a folder can be read, write or executed by you.

Even if Haiku operating system doesn't handle multiple users or any kind of "root" user, it's interesting to know how to change the access rights on a file.

Do you know the User Guide which is displayed by default on the Haiku desktop ?

Maybe not entirely, I will explain you why :)

Access rights on files

You might know that the User Guide is opening the HTML page corresponding to the user guide.

However the link used behind is /bin/userguide Let's review this file from a permission point of view.

Type in a Terminal the below command to display the details of the access rights :

ls -l /bin/userguide

You might notice the strange characters displayed at the beginning of the line returned :

- r-x r-x r-x

(0) (123) (456) (789) The meaning of each character from 0 until 9 is as below : (0) The first symbol indicates the file type :

• – : file
• d : directory
• l : link

(123) The symbols from 1 to 3 indicate the rights of the user on the file :

• « user » (u) : owner
  • « r » (4 / read) : read right (if « -«  then no right)
  • « w » (2 / write) : write right  (if « -«  then no right)
  • « x » (1 / execute) : execute right (if « -«  then no right)

(456) The symbols from 4 to 6 indicate the rights of the group on the file :

• « group » (g) : group
  • « r » (4 / read) : read right (if « -«  then no right)
  • « w » (2 / write) : write right (if « -«  then no right)
  • « x » (1 / execute) : execute right (if « -«  then no right)

(789) The symbols from 7 to 9 indicate the rights of others on the file :

• « other » (o) : others (all the users which are not the owner or not in the group)
  • « r » (4 / read) : read right (if « -«  then no right)
  • « w » (2 / write) : write right (if « -«  then no right)
  • « x » (1 / execute) : execute right (if « -«  then no right)

In the case of the /bin/userguide, the meaning is that :

• It's a file
• The user named "user" have read and execute permission
• The group named "root" has read and execute permission
• Everyone has read and execute permission

Now let's compare the "User Guide" on the Desktop which is just a link versus the /bin/userguide which is a command.

Copy the userguide command on the Desktop :

cp /bin/userguide /boot/home/Desktop

As you can see :

• The "l" character for "User Guide" indicates that it's just a link to "/boot/system/bin/userguide"
• The "-" character for /boot/home/Desktop/userguide indicates that it's a file and is executable ("x" right for user/group/others)

Now let's do some modifications on the "userguide" copied on the Desktop :

chmod u+r /boot/home/Desktop/userguide

Add (+) read right (r) to the user (u) on the file

chmod u-r /boot/home/Desktop/userguide

Remove (-) read right (r) on the user (u) on the file 

chmod 700 /boot/home/Desktop/userguide

Give all accesses (7) to the user and no access to the group (0) or to others (0).

For the details : 7 is corresponding to 4(r)+2(w)+1(x) while 0 indicates no right.

chmod o-rwx /boot/home/Desktop/userguide

Remove (-) the read right (r) the write right ( w) and the execution right (x) to others (o) 

chmod a+r /boot/home/Desktop/userguide

Add (+) the read right (r) to all (a).

All means : user (u) + group (g) + others (o).

chmod go+r /boot/home/Desktop/userguide

Add (+) read right (r) to the group (g) and to others (o).

Use case

Let's open the file "userguide" :

open /boot/home/Desktop/userguide

As you can see it will open the "User Guide" HTML page corresponding to your language.

Now let's remove the "execution" right on this file :

chmod u-x /boot/home/Desktop/userguide

If you open the file again :

Tada !

It's now opened in Styled Edit.

Do you know the reason ?

Well, as you can see, the content of this file is a bash script.

Removing the execution right, means that now it will not be possible to execute that script, that's why it's opened in a text editor :)

There's another way to change the permissions on a file.

Right click on it and select "Get info" :

As you can see there's a "Permissions" tab allowing you to change the owner/group/other rights :

Nice ?

To finalize this article, let's compare the differences between a link to "User Guide" versus the bash file corresponding to "userguide".

On the "Information" tab :

The first indicates it's a "Symbolic link" while the second indicates it's a "Text file".

On the "Permissions" tab :

The link can be read / modified / executed while the file can be read / executed.

On the "Attributes" tab :

The attributes for the link do not contain much information, while the bash script file is including an icon.

Please note that depending on the folder or file location, you don't have all the rights to change the permissions on it.

For instance the "/boot/system" is a system directory and you will not be able to change it.

The opposite in the "/system/non-packaged" folder : it's not a system directory, so you will be able to change the access rights.

I hope you have found this article useful, if you would like to share some information on that topic you can put a comment below.