What is umask in Linux?

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Umask stands for user mask or user file creation mask.Default permission or base permission give when a new file or folder is created in linux. In linux it is 022(0022)is default umask.

shakti@mydomain.com# umask
shakti@mydomain.com# 0022

Now we learn how to set new umask and the calculate the file permission over new file or folders.

Key Point :
Umask value for a folder is 000 to 777.
Umask value for a file is 000 to 666.

Decimal    Binary       Premissions       umask
0           000            ---            rwx
1           001	           --x            rw-
2           010            -w-            r-x
3           011            -wx            r--
4           100            r--            -wx
5           101            r-x            -w- 
6           110            rw-            --x
7           111            rwx            (none)

Calculate umask for folder.
1. First find the not for give umask.
2. Do logical AND with max permission
If we have umask is (023) then calculate the file permission over folder.
1. NOT(023) = 754
2. 777 AND 754 = 754
Shortcut method to calcuate umask is simply subtract umask from max value the you will get the actual value the folder have permissions.
777 – 023 = 754

Your comments are welcome to improve this post. Happy Learning 🙂

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