Chmod Symbolic Mode Permissions

Symbolic Notation

Symbolic notation is used to change the permissions of files and directories relative to their current permissions.

This tool can be used to explore how symbolic notations work.

To use this tool set the current octal value of your file permissions and then select from the checkboxes below to create the target permissions for your file(s).

Symbolic Value

File Permission's "Symbolic Value", or "Symbolic Notation", is a string made up of 10 characters that represents access granted to users on the system. Each "Symbolic Value" string is broken down into 4 sections. The file type (file or directory), Owner, Group, and Other in that order. The file is the first character (either d or -), while each of the subsequent groups (owner, group, and other) are represented by each subsequent cluster of three characters. In short, a "Symbolic Value" is the "string" based counterpart of a corresponding "Octal Value". 

How to change permissions in symbolic mode

• If you are not the owner of the file or directory, become superuser.

  Only the current owner or superuser can use the chmod command to change file permissions on a file or directory.

• Change permissions in symbolic mode by using the chmod command.

  $ chmod who operator permission filename

  who operator permission	who specifies whose permissions are to be changed, operator specifies the operation to be performed, and permission specifies what permissions are to be changed.
  filename	Specifies the file or directory.

   

   

• Verify that the permissions of the file have changed.

  $ ls -l filename

Common Chmod Symbolic Mode Permissions 

The chmod command is used to change the permissions of a file or directory. Here are the common chmod symbolic mode permissions:

1. r: This stands for "read" and permits open and read a file. On a directory, this permission allows you to list the directory's contents.
2. w: This stands for "write" and gives permission to modify a file. On a directory, this permission allows you to add, remove, and rename files in the directory.
3. x: This stands for "execute" and permits to run a file as a program. On a directory, this permission allows you to enter the directory and access its files and subdirectories.
4. a: This stands for "all" and refers to all users: the owner, the group, and others.
5. u: This stands for "user" and refers to the file or directory owner.
6. g: This stands for "group" and refers to the group that owns the file or directory.
7. o: This stands for "others" and refers to all other users not in the file's group.
8. +: This is used to add a permission to a file or directory.
9. -: This is used to remove a permission from a file or directory.
10. =: This is used to set permissions and overwrite the existing permissions.

For example, to add read (r) and write (w) permission to the owner (u) of a file, you would use the command chmod u+rw filename. To remove execute (x) permission from others (o), you would use the command chmod o-x filename.

Permissions and Corresponding Symbolic Representations

The table below displays both numeric values and symbolic representations for permissions.