Linux common Commands--file operations, permissions settings

1. Edit the file

VI aaa.txt    open aaa.txt file    Esc key         switch Edit and command mode    command mode input: (colon), you can enter the command    : S/  string 1/ String 2  Replace string 1 with string 2    : Wq! Save the file and exit    : Q!  Force exit file Editing    

2. View the contents of the file

cat aaa.txt       View        contents of aaa.txt file -5  aaa.txt   View the contents        of the first 5 rows of the Aaa.txt file -  aaa.txt  Show the contents of the last 10 lines of the Aaa.txt file   

3. Operation User and user group

su root      switch to root user    WhoAmI       View current logged-in user groups view current user's       group ID to see           uid and GID    Useradd      Add a new user (root)    passwd sa    set the SA user's password (under root)    passwd       Change Password    userdel      Delete User (root)     Groupadd G1       add G1 Group (root)    -G G1 SA  assigns SA user to G1 Group (root)

4. Set file permissions

751 temp    Sets 751 permissions to the Temp folder -rwxr-x--x    111101001     751
All represent a permission,

-rwxr-x--X,111 101 001,751  cannot type permission representation, permission level is the same, above 751 for the other 2 look also ok
PS is used to display the status of the current process

Permission Explanation:

-r-xr-xr--
101 101 1002 Binary
554
-RW--W---X
110 010 001
621
-rwxrwxr--
111 111 100
774
-R---W---x
100 010 001
421

Summary rule: R indicates that 4,w means that 2,x represents 1

Linux common Commands--file operations, permissions settings