builtins/line_loop_options.rb

tests/_examples/builtins/line_loop_options.rb in the metorex repository.

# `Array#join` joins a nested array with the same separator, however deeply
# they nest.
p ["a", "b", ["c", "d"]].join(" ")
p [1, [2, [3]]].join("-")
p [1, 2].join(",")
p [].join(",")

# `$FILENAME` names the file ARGF is reading, and `$.` counts the lines read.
one = "/tmp/metorex_lineloop_one.txt"
File.write one, "alpha\nbeta\n"
stream = ARGF.class.new one
p $.
stream.gets
p stream.lineno
stream.gets
p stream.lineno
stream.rewind
p stream.lineno
File.delete one

# A stream read to the end is closed, and cannot be put back to the start.
drained = ARGF.class.new "/tmp/metorex_lineloop_two.txt"
File.write "/tmp/metorex_lineloop_two.txt", "only\n"
drained.read
begin
  drained.rewind
rescue ArgumentError => problem
  p problem.message
end
File.delete "/tmp/metorex_lineloop_two.txt"

Output:

"a b c d"
"1-2-3"
"1,2"
""
0
1
2
0
"closed stream"