#!/usr/bin/awk -f

# Cut just the columns specified.
# usage awk -f columns.awk columns=one,two,five [header=2] [filenames]
# The input must contain a header line.
# This header contains column titles.
# All lines before the header are ignored.
# Eric Blossom - December 2003

BEGIN {
  header = 1;
  FS = "\t";
  OFS = FS;
}

1 == NR {
  temp = $0;
  n = split( columns, columnName, /[,;] */ );
  numberOfColumnsOut = n;
  if ( 0 == n ) {
    print "ERROR: columns not defined." | "./tostderr";
    exit 1;
  }
  $0 = temp;
}

FNR < header {
  next;
}

FNR == header {
  delete column;
  for ( i = 1; i <= NF; i++ ) {
    column[$i] = i;
  }
  next;
}

{
  n = 1;
  for ( i in columnName ) {
    if ( columnName[i] ) {
      value = "";
      if ( columnName[i] in column ) {
        value = $(column[columnName[i]]);
      }
      printf value;
    }
    if ( n < numberOfColumnsOut ) {
      printf OFS;
      n++
    }
  }
  print "";
}