https://github.com/akkartik/mu/blob/master/filesystem.mu

     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 ]