1 # example program: copy one file into another, character by character
 2 # BEWARE: this will modify your file system
 3 # before running it, put some text into /tmp/mu-x
 4 # after running it, check /tmp/mu-y
 5 
 6 def main [
 7   local-scope
 8   source-file:&:source:char <- start-reading null/real-filesystem, [/tmp/mu-x]
 9   sink-file:&:sink:char, write-routine:num <- start-writing null/real-filesystem, [/tmp/mu-y]
10   {
11     c:char, done?:bool, source-file <- read source-file
12     break-if done?
13     sink-file <- write sink-file, c
14     loop
15   }
16   close sink-file
17   # make sure to wait for the file to be actually written to disk
18   # (Mu practices structured concurrency: http://250bpm.com/blog:71)
19   wait-for-routine write-routine
20 ]