shift - adjust Shell arguments
Shift is used in Shell command files to shift the argument list left by
1, so that old $2 can now be referred to by $1 and so forth.
Shift is useful to iterate over several arguments to a command file.
For example, the command file
if $1x = x exit
pr -3 $1
prints each of its arguments in 3-column format.
Shift is executed within the Shell.