Permissions

• Every file has permissions that specify who can access the file and what they can do with it.

• Permissions are in groups of 3 - the first 3 are the user permissions (the login that owns the file); the next 3 are the group permissions (all logins in the same group as the owner of the file); the next 3 are the permissions for other(everyone else).

• Here is some sample output from ls -l

• So, tom is the owner of the file called tmp. That login id has read, write, and execute permission on the file.

• The group of the user who owns the file is group1. All login ids that belong to the group have read and write permission.

• All other login ids only have read permission on the file.

• Execute permission on a file means that it can be run - it is most likey a shell script or other program (i.e. perhaps an executable or a Perl script).

• Notice that tmp is a directory - how can you tell this?

• Execute permission on a directory means that you can cd to it.

• What do you think write permission on a directory means? How about read permission?