Run Multiple functions from an executable? - common-lisp

Question

I build CL executables as advised in the CL cookbook. I use the ASDF method with :entry-point
(asdf:defsystem #:thing
:serial t
:components ((:file "package")
(:file "thing"))
:build-operation "program-op"
:build-pathname "launch"
:entry-point "thing:main")
I added an entry point. Which is the main function. When I open (double click) my executable, the main function runs.
As my app has grown, i have multiple stand alone "main" operations.
Is this a sign for adding a UI or can i create executables that run different operations?

Answer 1

You can dispatch on the binary name, and get the latter with (uiop:raw-command-line-arguments).
Suppose I build a binary. Inside your thing:main function, we study how UIOP gets us the CLI args:
(format t "raw CLI args are: ~S~&" (uiop:raw-command-line-arguments))
(format t "CLI args are: ~S~&" (uiop:command-line-arguments))
If I call ./helloapp me, the values are:
raw CLI args are: ("./helloapp" "me")
CLI args are: ("me")
We can dispatch on the calling binary name from the main function.
(defun hello (args)
(format t "Hello ~a!~&" (first args)))
(defun goodbye (args)
(format t "Hello and bye ~a!~&" (first args)))
(defun main ()
(format t "raw CLI args are: ~S~&" (uiop:raw-command-line-arguments))
(format t "CLI args are: ~S~&" (uiop:command-line-arguments))
(if (search "goodbye" (first (uiop:raw-command-line-arguments))
:test #'equalp)
(goodbye (uiop:command-line-arguments))
(hello (uiop:command-line-arguments)))))
Creating links works:
$ ln -s helloapp goodbyeapp
$ ./goodbyeapp me
raw CLI args are: ("./goodbye-link" "me")
CLI args are: ("me")
var args are: ("me")
Hello and bye me!
ACK: I'm building on Ignis Volens' comment and learned a trick along the way.