How does the shell store information?

Like other programs, the shell stores information in variables. Some of these, called environment variables, are available all the time. Environment variables' names are conventionally written in upper case, and a few of the more commonly-used ones are shown below.

Variable	Purpose	Value
HOME	User's home directory	/home/repl
PWD	Present working directory	Same as pwd command
SHELL	Which shell program is being used	/bin/bash
USER	User's ID	repl

To get a complete list (which is quite long), you can type set in the shell.

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Use set and grep with a pipe to display the value of HISTFILESIZE, which determines how many old commands are stored in your command history. What is its value?