LINUX constant test instruction (update) __linux

This post is designed to record the instructions that are often tested under Linux.

1, chmod

The chmod command is used to change permissions for a file or directory. The common syntax is as follows:

chmod [who] [+ |-| =] [mode] File name

The meanings of the options in the command are:

U represents "User", which is the owner of a file or directory.
g means "same group of users", that is, all users who have the same group ID as the owner of the file.
o Represents "other (others) users".
a represents "all users". It is the system default value.

The action symbol can be:

+ Add a permission.
-Cancels a permission.
= gives the given permission and cancels all other permissions, if any.

The following is an analysis of the user rights for Linux files:

Examples are as follows:

Modify a.cpp for writable readable executable:

chmod 777 A.cpp

Delete A.cpp other groups can write executable, belong to the group executable:

chmod g-x o-wx A.cpp

Delete all (including owner, Group, others) executable:

chmod a-x a.cpp
or
chmod-x a.cpp

To set the owner-readable writable executable:

chmod u=rwx A.cpp

Note not o = 777!!!

To modify the properties of all CPP files:

chmod 777 *.cpp

Modify all file attributes (excluding subdirectories) in the directory to write-readable executable:

chmod 777 *.*

You can replace the folder name with the suffix name.

To modify all folder properties under the directory:

chmod 777 *

Replace the folder name with *.

To modify the current folder properties:

chmod 777.

Modify the directory/images/xiao to be writable and readable:

chmod 777/images/xiao

To modify all files and folders and subfolder properties in a folder to be writable and readable:

Chmod-r 777/images/xiao