https://github.com/akkartik/mu/blob/master/real-files.mu
 1 # example program: read a character from one file and write it to another
 2 # BEWARE: this will modify your file system
 3 # before running it, put a character into /tmp/mu-x
 4 # after running it, check /tmp/mu-y
 5 
 6 def main [
 7   local-scope
 8   f:num/file <- $open-file-for-reading [/tmp/mu-x]
 9   $print [file to read from: ], f, 10/newline
10   c:char, eof?:bool <- $read-from-file f
11   $print [copying ], c, 10/newline
12   f <- $close-file f
13   $print [file after closing: ], f, 10/newline
14   f <- $open-file-for-writing [/tmp/mu-y]
15   $print [file to write to: ], f, 10/newline
16   $write-to-file f, c
17   f <- $close-file f
18 ]