Under various UNIX and Linux operating systems, each file (folder is also considered a file) is read, write, run set permissions.
When using the ls-l command to list the file table, the following output is obtained:
-rw-r--r--1 Chen Users 2254 2009-06-13 14:35 hello.c
From the second word character rw-is that the user Chen has read, write right, no operation right,
The next r--indicates that the user group users only have read access, no running rights,
The last r--refers to other people (others) only read permission, no write right and run right.
This is the system default setting that can overwrite tt.htm, the same group of people and other people only have the right to read, no one has the right to run.
Read, write, run three permissions can be expressed in numbers, r=4,w=2,x=1. And the privilege combination can be added, such as rw=4+2=6,rwx=7
So, the rw-r--r--in the above example is represented by a number of 644. 777 is rwxrwxrwx, meaning that all users have the highest privileges.
The meaning of chmod 777