You can run Eshell scripts much like scripts for other shells; the main
difference is that since Eshell is not a system command, you have to run
it from within Emacs. An Eshell script is simply a file containing a
sequence of commands, as with almost any other shell script. Scripts
are invoked from Eshell with source, or from anywhere in Emacs
with eshell-source-file.
If you wish to load a script into your current environment,
rather than in a subshell, use the . command.