File permissions related operations under Linux

A permission Mask umask
Umask is chmod matching, a total of 4 (Gid/uid, owner, group rights, other user's rights), but usually use the latter 3, for example, you use chmod 755 file (at this time the permissions of this document is the main read (4) + write (2) + execute (1), The same group and other users have read and write permissions)

The role of two umask
By default the Umask value is 022 (can be viewed with the umask command), at this point you establish the default permissions of the file is 644 (6-0,6-2,6-2), the default permissions for the established directory is 755 (7-0,7-2,7-2), you can verify with Ls-l OH Now you should know the use of umask, it is to control the default permissions, do not make the default files and directories have a full set of
Three modified umask values
Once you know the role of umask, you can modify the value of Umask, for example: Umask 024 The default permissions for files and directories that are created later are 642,753.
Four Save the Umask value to the environment file
To modify the value of umask for a long time, you can write it into/etc/profile or ~/.profile or ~/.bash_profile, and you should know what these files are for?
Do you know what the default attributes will be when you create a new file or directory? Oh! It's about the umask! So what's umask doing? Basically, umask is specifying "the default value of the property when the user is creating the file or directory", so how do you know or set umask? His specified condition is specified in the following way: syntax:

[Root @test root]# umask
0022
[[email protected] test]# umask 002 <== after 3 numbers!
[Email protected] test]# umask
0002
Description: View umask value for direct input umask, and set it? That's right! is umask after three numbers! So how do you specify it? It is mainly related to the file attributes of Linux (that nine properties, R, W, X), and is the example of the relationship with fractions, and the following rules are supplemented:
If the user is set up as "file" then the default "no executable (x) project", that is, only the RW two items, which is the maximum of 666 points
–rw-rw-rw-
If the user is created as a "directory", the default is open for all permissions, which is 777 points, because X is related to whether it can be entered into this directory.
Drwxrwxrwx

Add:

"chmod +x file name" adds executable permissions to the file
"Chmod-x file name" Removes executable permissions for files
...
...
We can comprehend by analogy.

File permissions related operations under Linux