The umask command in Linux is used to set default permissions for files and directories created by the user. It specifies the permissions that should not be given to newly created files or directories by performing a bitwise AND with the bitwise complement of the umask value¹.

Understanding Umask

The umask value is a three-digit octal number that represents the permissions to be masked out. Each digit corresponds to the permissions for the owner, group, and others, respectively. The default permissions for files are 666 (read and write for all), and for directories, they are 777 (read, write, and execute for all). The umask value is subtracted from these defaults to determine the final permissions¹.

Example

To check the current umask value, simply type:

This might output something like 0022, which means that write permissions are blocked for the group and others².

To set a new umask value, use: