This built-in command takes one number as argument and shifts the positional parameters to the left by that number. The positional parameters from n + 1 to $# are renamed to variable names from $1 to $# - n + 1. The first n positional parameters are thrown away.
If the number is not present, it is assumed to be 1.
If n is zero or greater than $#, the positional parameters are not changed and the command has no effect.