Linux permission modification command

grammar:

　　chmod value filename

 

example:

　　chmod 644 mm.txt

　　After the command is executed, the permission value of the file mm.txt is rw-r--r--

 

Detailed explanation:

　　      The permissions are divided into three types: read, write, and execute, which are represented by the letters r w x and have different weights;

　　Its permissions are r=4, w=2, x=1

　　4+2+1=7 for rwx attributes;
　　4+2=6 for rw- attributes;
　　4+1=7 for rx attributes.