file_binary.rb

# Excerpt from ptools gem

# Returns whether or not +file+ is a binary non-image file, i.e. executable,
# shared object, ect. Note that this is NOT guaranteed to be 100% accurate.
# It performs a "best guess" based on a simple test of the first
# +File.blksize+ characters, or 4096, whichever is smaller.
#
# By default it will check to see if more than 30 percent of the characters
# are non-text characters. If so, the method returns true. You can configure
# this percentage by passing your own as a second argument.
#
# Example:
#
#   File.binary?('somefile.exe') # => true
#   File.binary?('somefile.txt') # => false
#-- 
# Based on code originally provided by Ryan Davis (which, in turn, is
# based on Perl's -B switch).
#
def self.binary?(file, percentage = 0.30)
  return false if image?(file)
  return false if check_bom?(file)
  bytes = File.stat(file).blksize
  bytes = 4096 if bytes > 4096
  s = (File.read(file, bytes) || "") 
  s = s.encode('US-ASCII', :undef => :replace).split(//)
  ((s.size - s.grep(" ".."~").size) / s.size.to_f) > percentage
end