Understanding Access Control List with some Examples

To understand the access control we will look at some examples based on the Unix system. If you use the ls –l command in the Unix command prompt you will be listed the files and the directories in the default directory and you can also see the permissions available for the different files for the owner, group, and others. For example if a file that is listed with that command has been listed as below,

- rw- rw-r-- sam mktg flybird.gif

The first ‘-‘ indicates that it is a file. If there is a ‘d’ in the first place it indicates it is a directory. The first three letters indicate the permission for the owner of the file. The owner is ‘sam’ in this case. ‘r’ indicates that the owner has the read permission and an ‘w’ indicates that he has the write permission too.

If there is an ‘x’, it indicates that the user has the execute permission. The next three letters are the permissions for the group he belongs to and the last three letters are the permission for ‘others’. You can change the permission using the ‘chmod’ command in the command prompt.