#!/usr/bin/perl# Mark Claypool# Last significantly modified: December, 2001# This program prints out fields of an indicated column.# The columns are numbered 0, 1, 2, 3 ...require 'getopts.pl';&ParseCommandLine;$line = <STDIN>;while ($line) {  $line =~ s/^\s+//;		# remove initial white-space  $line =~ s/\s+/ /g;		# turn double-space into single space  @word = split($split,$line);	# columns will then be $1, $2, $3 ...  $i =0;  while ($i <= $#col) {    print "@word[@col[$i]]\t";    $i += 1;  }			  print "\n";  $line = <STDIN>;}exit;######################################################################## ParseCommandLine# check for the right number of command line arguments# print usage message and quit if there is an error# global variables are @colsub ParseCommandLine   {  # get token to split on  &Getopts('t:');  if ($opt_t) {    $split = $opt_t;  } else {    $split = '\s+';  }  # get columns  while ($#ARGV >= 0) {    $arg = shift(@ARGV);    if ($arg =~ /^(\d+)/) {      push(@col, $1);    } else {		      &usage;    }  }  if ($#col < 0) {    &usage;  }}		########################################################################### usage# print a usage maessage and quitsub usage{    print STDERR "column: print fields from an indicated column\n";    print STDERR "Usage: column <flags>, where flags are:\n";    print STDERR "       [-t str]\ttoken to use as a separator (default is white space)\n";     print STDERR "       {# [#...]}\tcolumn(s) to print, numbered 0,1,2...\n"; 	exit;}