Modifying file user attributes in Linux

Chgrp command

Function: Change the group to which a file or directory belongs.

Syntax: chgrp [Option] group filename?

This command changes the user group to which the specified file belongs. The Group can be either the user group ID or the group name of the user group in the/etc/group file. A file name is a list of files separated by spaces to change the group. Wildcards are supported. If the user is not the owner or super user of the file, the file group cannot be changed.

The options of this command are as follows:

-R recursively changes the group of all subdirectories and files in a specified directory.

CHOWN command

Function: Modify the owner and group of a file or directory. This command is also very common. For example, if the root user copies a file to Xu, the root user should set the owner of the file to Xu to allow Xu to access the file. Otherwise, user Xu cannot access this file.

Syntax: chown [Option] user or group file

Note: chown will change the owner of a specified file to a specified user or group. Users can be user names or user IDs. A group can be a group name or group ID. Files are separated by spaces to change the permission list. Wildcards are supported.

The options of this command are as follows:

-R recursively changes the owner of all subdirectories and files under a specified directory.

-V: displays the work done by the CHOWN command.

Chmod

Permission: All Users

Usage: chmod [-CFVR] [-- help] [-- version] mode file...

Note: The file calling permissions for Linux/Unix are divided into three levels: file owner, group, and others. Chmod can be used to control how files are called by others.

Parameters:

Mode: permission setting string in the following format: [ugoa...] [[+-=] [rwxx]...] [,...], where

U indicates the owner of the file, G indicates that the owner of the file belongs to the same group, O indicates that the owner of the file belongs to other people, and a indicates that all three are.

+ Adds a permission,-Indicates canceling the permission, and = indicates a unique permission.

R indicates that the file can be read, W indicates that the file can be written, and X indicates that the file can be executed only when the file is a subdirectory or the file has been set to executable.

-C: if the permission of the file has been changed, the change action is displayed.

-F: Do not display an error message if the file permission cannot be changed.

-V: displays details of permission changes.

-R: Change the permissions of all files and sub-directories in the current directory in the same way (that is, change one by one in the way of delivery)

-- Help: displays auxiliary instructions

-- Version: displays the version.

Example: Set the file file1.txt to readable by all users:

Chmod Ugo + R file1.txt

Set file1.txt to readable:

Chmod A + R file1.txt

Set file1.txt and file2.txt as the owner of the archive, which can be written to the same group to which the archive belongs, but not to others:

Chmod ug + W, o-w file1.txt file2.txt

Set ex1.py to only the owner of the file to execute:

Chmod U + x ex1.py

Set all files and subdirectories in the current directory to be readable by anyone:

Chmod-r a + R *

In addition, chmod can use numbers to indicate permissions, such as chmod 777 file.

Syntax: chmod ABC File

Each A, B, and C is a number, indicating the permissions of the user, group, and other respectively.

R = 4, W = 2, x = 1

If you want the rwx attribute, 4 + 2 + 1 = 7;

If the RW-attribute is required, 4 + 2 = 6;

If you want the R-x attribute, 4 + 1 = 7.

Example:

Chmod A = rwx File

And

Chmod 777 File

Same effect

Chmod ug = rwx, O = X file

And

Chmod 771 File

Same effect

If chmod 4755 filename is usedProgramRoot permission