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
example:
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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