[LINUX] I tried to summarize the umask command
Introduction
There are various introductions of umask command and mask value on the net, I will post an article because I found it difficult to use logical sum, logical product, and bit inversion.
What is the umask command?
When creating a new file or directory Decide what kind of access rights (permissions) to mask.
You can ** mask ** for each ** user **. By the way, umask is an abbreviation for user mask.
What is a mask?
In the first place, what is a mask means "cover". The mask we wear also "covers" the mouth, doesn't it?
How umask and mask values work
Let's look at the relationship between the umask command and the mask value. Originally, when creating a new file or directory, all privileges (777) are granted. By subtracting the mask value there, the access right actually granted is determined.
. 777 ← Access right when creating a new file or new directory -) 022 ← umask command execution result (mask value)
. 755 ← umask -S execution result ... *
** When creating a file, the x right is deprived from the access right of * It will be 644 (rw-r--r--). ** **
Actual machine operation
reference
The thousands digit "0" that is output when the umaks command is executed represents a special access right.
- 4：SUID
- 2：SGID ―― 1: Sticky bit --0: No special access rights
Summary
If you want to change the access right when creating a new file or directory, use the umask command. X rights are deprived when creating a file, so if you want to execute it as a program file Grant X rights with the chmod command. ~~ I hope the distribution of masks will return to normal soon ... ~~
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