umask

In computing, umask is a command that determines the settings of a mask that controls how file permissions are set for newly created files. It also may refer to a function that sets the mask, or it may refer to the mask itself, which is formally known as the file mode creation mask. The mask is a grouping of bits, each of which restricts how its corresponding permission is set for newly created files. The bits in the mask may be changed by invoking the umask command.