Editing File-system permissions (section)

====Symbolic notation====
Symbolic notation is used in the long output format of command <code>ls -l</code>.

The first character of the output indicates the [[Unix file type]] which is not a  permission even though its next to the permissions information. The remaining nine characters represent the grants for the user, group and others classes as groups of operation grants for read, write and execute. An operation is denied when shown as a dash or granted when shown as {{code|r}} for read, {{code|w}} for write or {{code|x}} for execute. 

Examples:
* <code>-rwxr-xr-x</code>: initial {{code|-}} indicates a regular file, next three {{code|rwx}} indicate that user class has all permissions and group and others classes (both {{code|r-x}}) have only read and execute
* <code>crw-rw-r--</code>: initial {{code|c}} indicates a character special file, user and group classes (both {{code|rw-}}) have read and write permissions and others class ({{code|r--}}) has only read permission
* <code>dr-x------</code>: initial {{code|d}}) indicates a directory, user class ({{code|r-x}}) has read and execute permissions and group and others classes (both {{code|---}}) have no permissions

To represent the  ''setuid'', ''setgid'' and ''sticky/text'' attributes, the character in the third position for a class is modified; even though this position is otherwise only for execute and even though these attributes affect the file without concern for class. The setuid attribute modifies the execute character for the user class, the setgid attribute modifies the execute character for the group class, and the sticky or text attribute modifies the execute character for the others class. For setuid or setgid, <code>x</code> becomes <code>s</code> and <code>-</code> becomes <code>S</code>. For the sticky or text attribute <code>x</code> becomes <code>t</code> and <code>-</code> becomes <code>T</code>. For example <code>-rwsr-Sr-t</code> indicates a regular file, user class has read, write and execute permissions; group class has read permission; others class has read and execute permissions; and which has ''setuid'', ''setgid'' and ''sticky'' attributes set.

Some systems show additional permission features:
* {{code|+}} suffix indicates an access control list that can control additional permissions
* {{code|.}} suffix indicates an [[SELinux]] context is present.  Details may be listed with the command <code>ls -Z</code>
* {{code|@}} suffix indicates [[extended file attributes]] are present