Ruby script to split one file into multiple files, using Markdown h1 headers

mdsplit.rb

#!/usr/bin/env ruby

if ARGV.empty?
  puts "Usage: #{__FILE__} filename [directory]\n\n"
  puts "The file 'filename' will be split at each Markdown h1 ('# ') header. If"
  puts "'directory' is specified, it will be used as the output directory."
  puts "Otherwise files will be written to the current directory.\n\n"
  exit(2)
end

out_dir = ARGV[1] || '.'
out_files = {}
out_file = ""

puts "Writing to directory #{out_dir}"

f = File.open(ARGV[0])
f.each_line do |l|
  if l[0,2] == "# "
    out_file = l[2, 99]
    print "--> #{out_file}"
    out_files[out_file] = ""
  elsif out_file != ""
    out_files[out_file] << l
  end
end
out_files.each do |filename, body|
  IO.write(out_dir + "/" + filename.strip, body.lstrip)
end

This script splits a file into multiple pieces using # Markdown headers as the split points and the filenames:

# file1.foobar.md
Lorem ipsum blah blah blah
# file2.foobar.md
Lorem ipsum etc so on and so forth

This is useful if you have some reason to create a whole bunch of short files all at once. I wrote it for a specific need in documentation, but have also used it for creating BBEdit clippings.