namecut

#!/usr/bin/env ruby

$doc = %{
namecut [column names and/or 1-based indexes]

Assume first line is a header.
Those columns are extracted (like sql select).
Like 'cut' but with names; and jankier.
}

if STDIN.tty?
  STDERR.puts $doc.strip
  exit 1
end

colnames = $stdin.readline.chomp.split("\t")
cols = ARGV
problems = []
col_inds = cols.map { |c|
  if c =~ /^\d+$/
    c = c.to_i
    raise "bad column number (1-indexed): #{c}" if c<=0 || c > cols.size+1
    c -= 1
  else
    c = $1 if c =~ /^-f(.*)/
    raise "don't support cut's full -f syntax yet" if c =~ /,/
    colnames.index(c) or problems << c
  end
}
if problems.size > 0
  problems.each{|problem| $stderr.puts "No column with name: #{problem}"}
  exit -1
end

puts col_inds.map{|i| colnames[i]}.join("\t")

$stdin.each do |line|
  parts = line.chomp.split("\t")
  puts col_inds.map{|i| parts[i]}.join("\t")
end