perlcut

#!/usr/bin/perl -w

use strict;
my $joinchar = ' ';
main();

###################
# cut using perl's split rather than cut's single char
#	NOTE: Because we allow splitting by regexen, we always join by spaces by default.
# TODO: Add a mode to split by headers
#	Support more of cut's options
#	Do we really want to use perl's 0-based indexing, or should we correct to cut's 1-based?
###################

sub main
{
my ($splitter, $fieldspec) = handle_args(@ARGV);

while(my $line = <STDIN>)
	{
	chomp $line;
	my @parts = split(/$splitter/, $line);
	spit_it_out($fieldspec, @parts);
	}
}

sub spit_it_out
{ # Not particularly proud of this part. Might need to redo it entirely.
my ($fields, @parts) = @_;

# Possible forms of $fields:
# number
# number-number
# -number
# number-
# number,number,number
if($fields =~ /^(\d+)$/)
	{
	print $parts[$1] . "\n";
	}
elsif($fields =~ /^(\d+)-(\d+)$/)
	{
	print @parts[$1..$2] . "\n";
	}
elsif($fields =~ /^-(\d+)$/)
	{
	print @parts[0..$1] . "\n";
	}
elsif($fields =~ /^(\d+)-$/)
	{
	print @parts[$1..$#parts] . "\n";
	}
elsif($fields =~ /^\d+,\d+/) # Note that we do not capture - we want to actually use split here.
	{
	my @partlist = split(',', $fields);
#	eval("print join('$joinchar', \@parts[" . $fields . "]);");  # There's got to be a better way to do this...
#	print "\n";
	print join($joinchar, @parts[@partlist]) . "\n";
#	print @parts[@partlist] . "\n";
	}
else
	{die "Invalid field specifier [$fields]\n";}
}

sub handle_args
{
my @args = @_;
my ($has_spec, $has_fields) = (0,0);
my ($splitter, $fields);

if(@args != 2)
	{usage();}

foreach my $arg (@args)
	{
	if($arg =~ /^-d/)
		{
		$arg =~ s/^-d//;
		$arg =~ s/^"//; # Any beginning quote
		$arg =~ s/"$//; # Any ending
		$splitter = $arg;
#		print "D: Accept splitter of [$splitter]\n";
		$has_spec++;
		}
	elsif($arg =~ /^-f/)
		{
		$arg =~ s/^-f//;
		$fields = $arg; # Gotta really parse the heck out of this later
		$has_fields++;
		}
	}
if( (! $has_fields) || (! $has_spec) )
	{usage();}

return ($splitter, $fields);
}

sub usage
{
die "Usage: pcut -dSPEC -fFIELDS\n";
}