Introduction to Linux system permissions (1)

Introduction to Linux system permissions (1) Linux system permissions:
(1) A single file has three groups: users, groups, and others.
Each group has three permissions: Read R, write W, and execute x
That is to say, a file has nine permission attributes.
From left to right, one to three are [users], four to six are [groups], and seven to nine are [others].
For example, if you open any file using the rootexplorer manager, you can see its permission: RW-r -- rwx.
This means that [users] have read and write permissions on them, [groups] have read permissions, and [others] have read and write execution permissions.
(2) Correspondence between permissions and numbers
Many times, in order to easily write scripts and use terminals, people use numbers to indicate the permissions of files! (For example, in Android development You can use "chmod 777 file path" to change the File Permission to read and write for all groups .)
Correspondence between numbers and permissions:
Read r = 4
Write W = 2
Run x = 1
A total of three numbers represent the permissions of the three groups. The size of each number is equal to the sum of the three permissions contained in each group.
For example, if the permission of a file is RW-rwx-r-X, the number of the file is 675.
Indicates [user] Reading and Writing [group] Reading and Writing execution [other] Reading and Writing execution.