Umask, or user file-creation mode mask, is a fundamental concept in Linux and Unix systems that defines the default permissions for new files and directories. Understanding and checking umask values is crucial for system security and file management.

Understanding Umask

The umask value is a set of permissions that the system automatically subtracts from the default permissions when a new file or directory is created. For files, the default permission is typically 666 (read and write), and for directories, it's 777 (read, write, and execute). The umask value is subtracted from these defaults to get the actual permissions set on new files and directories.

For example, if the umask value is 022, new files will have permissions of 644 (default 666 - umask 022), and new directories will have permissions of 755 (default 777 - umask 022). This means that the owner can read and write the files, while others can only read them.

Checking Umask Values

To check the umask value for the current user, you can simply use the umask command without any arguments: