Compute SHA1 hash of the file given as first argument. Reads big files in chunks to avoid using all the available memory.

sha1.rb

require 'openssl'

file_name = ARGV.first

digest = OpenSSL::Digest::SHA1.new

file = File.open(file_name, "rb")
until file.eof?
  print "#"
  digest.update file.read(2**24)
end
file.close
print "\n"
print digest.hexdigest