How Linux Works

File Modes and Permissions

Every Unix file has a set of permissions that determine whether you can read, write, or run the file. Running ls -l displays the permissions. Here's an example of such a display:

-rw-r--r-- 1 juser  somegroup    7041 Mar 26 19:34 endnotes.html

The first column represents the mode of the file, and it is shown in bold. The mode represents the file's permissions and some extra information. There are four parts to the mode; Figure 1-1 on the next page illustrates the pieces.

Figure 1-1. The pieces of a file mode

The first character of the mode is the file type. A dash (-) in this position, as in the example, denotes a regular file, ...