lns.rb

#!/usr/bin/env ruby

# Save this to ~/bin/lns then never worry about the -s option and argument order
# for ln again

a,b = ARGV[0..1]
abort "provide source and dest, in any order" unless ARGV.size == 2

if File.exist?(a) && File.exist?(b)
  abort "both files exist"
elsif File.exist?(a)
  exec "/bin/ln", "-s", a, b
elsif File.exist?(b)
  exec "/bin/ln", "-s", b, a
else
  abort "neither file exists"
end