Review the content of the previous section:
1. Enter the directory: cd command
2. Create a directory: mkdir command
3. Delete a directory: rmdir command
4. File and directory copy: cp
Homework: Create directories test1, test2, create a test1.txt file in test1, and then copy the test1.txt file to the test2 folder
mkdir test1
mkdir test2
cd test1
touch test1.txt
cp test1.txt /test2
Contents of this section:
1. File/ directory details
When you use the ll command to view file/directory details, you can see information similar to the following
I used the red box to divide this information into 7 columns, which are explained below
First column: file type and permissions
There are a total of 10 horizontal lines, the first one represents the file type, commonly used file types:
d: folder
-: Normal file
l: link (windows-like shortcut)
b: block device files (such as hard disks, optical drives, etc.)
p: pipe file
c: character device file (such as serial port devices such as cats)
s: socket file/data interface file (for example, a mysql.sock file will be generated when a MySql server is started)
The last 9 are in groups of 3 to represent the owner of the file, all groups of the file, the permissions of other users, and the possible values of permissions:
r=read attribute //value=4
w=write attribute //value=2
x=execute attribute //value=1
When a position is empty, - is displayed, indicating that this permission is not available.
Second column: the number of connections
All files except directory files have a link count of 1
The number of connections of directory files is the total number of other directories in this directory + 2. For example, if directory a contains directories b and c, the number of links in directory a is 4.
Third column: file owner
Fourth column: file all groups
Fifth column: file size
Column 6: Last modification time
Seventh column: file name
2. Change file permissions: chmod command
Use u, g, o in the permissions to represent the file owner, owning group, and others, respectively. The permissions are represented by rwx, the + sign for adding permissions, the - sign for deleting permissions, and the = sign for specifying permissions.
Chmod u+w filename #indicates adding write permission to the file owner
Chmod uw filename # means to delete the write permission of the file owner
Chmod u=rwx filename # means to set the permissions of the file owner to readable, writable, executable
Chmod u+w,g+w #filename #Indicates that the file owner adds write permission, and all groups add write permission
To set permissions for everyone at the same time, it can be represented by numbers, rwx is represented by 7, r- is represented by 4, -w- is represented by 2, --x is represented by 1.
Chmod 741 filename #Indicates that the owner has read, write and execute permissions, all groups have read permissions, and others have execute permissions.
Taking test.txt as an example, the default permissions are as follows:
Now change the permissions, add execute permissions to the owner, add write permissions to all groups and others, execute
chmod u+x,g+w,o+w test.txt
Similarly, we can also use numbers to modify permissions. For example, to change the permissions of test.txt to u, g, and o have rwx permissions, you can use chmod 777 test.txt
Finally, change the test.txt permission to the original state, chmod u=rw,g=r,o=r test.txt
If you want to change the permissions of the directory and its subfiles, you need to use the -R parameter
Take the test folder as an example, you can see the default permissions:
Modify the permissions of the directory to g with w permissions
Chmod –R g+w test
Other operations are the same as the file, and finally change the permission of test to the default, execute chmod –R gw test
3. Change the file owner: chown command
Basic usage chown owner: own group filename, or chown -R owner: own group directory name
For example, to modify the owner of the file test.txt to user1, use: chown user1 test.txt
To modify the owning group of the file test.txt to user1, use: chown :user1 test.txt
To modify the owner and the owning group at the same time, use: chown user1:user1 test.txt
To modify the ownership of a directory and its sub-items, you need to use the -R parameter. For example, to modify the owner of the directory test and sub-files to be user1, use: chown –R user1 test
4. Change the file owning group: chgrp command
The basic user is similar to chown, except that this command only modifies all groups of the user. The basic usage is chgrp group name file name, or chgrp -R group name directory
Homework: Create a file test.txt, modify the file permissions to the owner with read, write and execute permissions, all groups have read and write permissions, others have read permissions, change the owner of this file to user1
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