umask — change permissions mask then chain
umask {mask} {next-prog}
Most shells have a built-in umask command that does not chain and has additional interactive functionality. See the manual for each individual shell for its built-in command. This command is more commonly used with exec(1) and nosh(1).
umask is a chain-loading utility that changes its permissions mask to
mask and then chain loads to next-prog with the execvp(3) function.
next-prog may contain its own command line options, which umask will ignore.
The mask is a number, and follows the C language conventions. Conventionally masks are specified in octal, which in the C language is specified by a leading 0.