#!/usr/bin/env python

# Cut just the columns specified.
# usage: python columns.py "col1,col2" [filenames]
# The input must contain a header line.
# This header contains column titles.
# All lines before the header are ignored.
# Eric Blossom - October 2004

# BUGS:
# How do we optionally specify header line on the command line?
# Can we use keywords on the command line? e.g. -columns=one,two -header=3

from fileinput import input
import string
import sys

headerLine = 1
columns = ""

nargs = len( sys.argv )
if nargs < 1:
   print >>sys.stderr, 'usage: python columns.py "col1,col2" [filenames]'
else:
   columns = sys.argv[1]
   del sys.argv[1]


columnTitle = string.split( columns, "," )
FS = "\t"
lineNumber = 0

for line in input():

    line = string.strip( line )
    field = line.split()

    lineNumber += 1
    if headerLine == lineNumber: # then we expect the column titles.
       iCols = [ field.index( x ) for x in columnTitle if x in field ]
       if len( iCols ) < 1:
          print >> sys.stderr, 'Whoa: Seems we are missing a header line.'

    out = [ field[x] for x in iCols ]
    if 0 < len( out ):
       print string.joinfields( out, FS )