What is umask and how is umask set | all about umask

what is umask (unix)

umask is nothing but user file-creation mask, which will decide the file permission for a newly created file in Unix.

Where is default UMASK set

umask can be set at

/etc/profile
or
~/.bashrc  (~ is your home directory)

How to set umask

umask command will display the default umask value set
umask <value> will the the umask
ex :- umask 022

I will explain a bit on this

calculate file permission for 022
Default file permission       : 666
Subtract umask value         : 022 (-)

Permission for new file     : 644 (rw-r–r–)

Calculate directory permission for 022
Default dir permission         : 777
Subtract umask value          : 022 (-)

Permission for new file      : 755 (rwxr-xr-x)

Why umask is used

This is an extra step of security which avoid accidental world write permissions (777) or unnecessary permissions granted to the newly created files and directories.

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