3.0.1 Hello World

Our first program is the typical Scheme "hello world" program. Put the following code in a file called hello.scm (this can be find in ‘examples/scheme/hello.scm’).

#!/usr/local/bin/guile -s
!#

(display "hello world")
(newline)

Then run guile on it. One way to do so is to start up guile and load this file:

<shell-prompt> guile
guile> (load "hello")

Another way is to make the file executable and execute it directly. Notice how Guile recognizes a -s option which tells it to run a script and then exit. Guile also has a new type of block comment enclosed by #! and !#, so that you can make executable Scheme scripts with the standard UNIX #! mechanism.

In the given example, the first line is used to invoke the Guile interpreter (make sure you correct the path if you installed Guile in something other than /usr/local/bin). Once Guile is invoked on this file, it will understand that the first line is a comment. The comment is then terminated with !# on the second line so as to not interfere with the execution mechanism.