A detailed explanation of Linux umask functions

The Umask function in Linux is used primarily to mask access permission that is not appropriate for new files or directories when creating new files or directories.

There are 9 kinds of access permission for files, respectively: rwxrwxrwx

They represent: User Read user Write user Execute Group read Group write group perform other read other write other execution

The rules for shielding are as follows:

1. No matter how much the shielding code is,

• The newly created file does not have permission to execute by default.

• The newly created directory has executable permission by default.

2. The format of the screen code is octal format, a total of three octal number. You can set the following 002 or 022 or ...

3. Each of these octal is represented by three digits, namely, read-write execution

4 2 1

For example, 002 is represented in binary as: 0 0 0--0 0 0--0 1 0

4 2 1 4 2 1 4 2 1

4. The resulting file is the umask value of the allowable permission, namely

For file: ~002 = 664 (the access rights that the newly created file should have)

For directory: ~002 = 775 (The access rights that the newly created directory should have)