File permissions are one of the strengths that the Unix world has had over it's Windows contemporaries. Permissions are a means to control access to information on a computer, on a per file. There are several layers of control, and these are discussed below.

For purposes of this series of tutorials, I've been using a free FTP program called Core FTP Lite to upload files to my server. I am using this program to describe my examples.

Ok, first, let's say we have some files sent to a server.

We are discussing load scripts in general here, and certainly for many scripts, the creators can also specify certain 'permissions' that need to be set for the scripts to function properly. Let's take a look at a set of files on a server. In Core FTP Lite, the file server are shown in the right pane. Select one and click the right mouse button on file If you use a different emphasis FTP client, I hope the layout is very similar.

Run the mouse to the bottom of the menu and select the item labeled "Properties." Click about this option, and another box will appear.

You will see that the file in question (in this case a directory) is being shown in the "File" at the top of the screen.

What we are really interested in, if the tick boxes in the bottom half of the screen. These privileges keep the file 'or' permission 'for this file or directory.

There are three types of 'permissions' available.

* User – which means that the person is signed on to set permissions

* Group – which means a specific group of users to whom the file access has been granted

* World – which means everyone.

Within these groups of users, there are 3 distinct types of Permissions

* Read – which means that the permission to read a file but not change it or run it

* Write – which means permission to write to a file and change it

* Run – which means permission to execute a file, which is important in the case of scripts, for example.

Permissions are sometimes called by these names (read, write, execute), but are more commonly referred to using letters rwx '. In , permissions are often referred to by a single
number '755 ', for example. In the photo above, you'll see a value box. This is the number to be mentioned. How is this number composite? Well, let me explain.

Read

User 400

Group 40

World 4

Write

User 200

Group 20

World 2

Run

User 100

Group 10

World 1

Each value of each configuration is shown. Try them, marking them, and see the number in the "Value field change 'in accordingly.

So, let's look at a real example

See how the number 755 is composed? Add up the individual values of the table value and see.

So hopefully you can see that the setting file permissions with the right tool is not difficult at all.

Charlie Cory worked or many years running a HelpDesk for a software house, and has experience in many operatng systems and technologies. The online aticle contains many pictures which help bring this tutorial to life.

Setting file permissons

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