Change file or directory permissions. In the UNIX system family, the file or directory permission control is divided into three general permissions: read, write, and execute, and three special permissions are available for use, combined with the owner and the group to manage the permission range. You can Use the chmod command to change the permissions of files and directories, using either text or Number code. The notation connection permissions cannot be changed. You can change the permissions on the notation connection. The changes will apply to the connected source file. The scope of permissions is expressed as follows:

u: User, that is, the owner of the file or directory.

g: Group, that is, the group to which a file or directory belongs.

o: Other: indicates that all users except the file or directory owner or the group to which the file or directory belongs belong to this range.

a: All, that is, all users, contain the owner, group to which the user belongs, and other users.

The permission code section is listed below:

r: read permission. Number is codenamed "4".

w: write permission. Number is codenamed "2".

x: Execute the or switchover permission. The Number code is "1".

- : does not have any permission. The Number code is "0".

s: Special? b> Function explain: Change permissions on files or directories.