File input/output is part of Short Circuit's Console Program Basics selection.
Task

Create a file called   "output.txt",   and place in it the contents of the file   "input.txt",   via an intermediate variable.

In other words, your program will demonstrate:

   how to read from a file into a variable
   how to write a variable's contents into a file


Oneliners that skip the intermediate variable are of secondary interest — operating systems have copy commands for that.




set in [open "input.txt" r]
set out [open "output.txt" w]
# Obviously, arbitrary transformations could be added to the data at this point
puts -nonewline $out [read $in]
close $in
close $out