Understanding Permissions

In the output of ls -l the file permissions are shown right after the filetype, as three groups of three characters each, in the order r, w and x. Here is what they mean. Keep in mind that a dash represents the lack of a particular permission.

Permissions on Files

Permission	Description
`r`	Stands for read and has an octal value of 4. This means permission to open a file and read its contents.
`w`	Stands for write and has an octal value of 2. This means permission to edit or delete a file.
`x`	Stands for execute and has an octal value of 1. This means that the file can be run as an executable or script.

Permissions on Directories

Permission	Description
`r`	Stands for read and has an octal value of 4. This means permission to read the directory’s contents, like filenames. But it does not imply permission to read the files themselves.
`w`	Stands for write and has an octal value of 2. This means permission to create or delete files in a directory, or change their names, permissions and owners. If a user has the write permission on a directory, the user can change permissions of any file in the directory, even if the user has no permissions on the file or if the file is owned by another user.
`x`	Stands for execute and has an octal value of 1. This means permission to enter a directory, but not to list its files (for that, the r permission is needed)