#!/usr/bin/perl 
#
# usage: perl shiftsnap.pl shift snapfiles 
#
# e.g. perl shiftsnap 103 snap.*.sgi changes all picture names
# from snap.x.sgi to snap.x+103.sgi
#
# (Warning: will overwrite snap.x+103.sgi if it exists already!)
#
# Note that imagefiles have to be of the form snap.<digits>.<ext>
#
# Dinoj Surendran 12 Feb 03 dinoj@cs.uchicago.edu

($shift,@imagefiles) = @ARGV;

if ($shift < 0)
{
    for ($i = 0; $i < $#ARGV; $i++)
    {
	($sn, $num, $ext) = split /\.+/ , $imagefiles[$i];
	$a = $num+$shift;
	$nufile = $sn.".".$a.".".$ext;
	$cmd = "mv ". $imagefiles[$i]." $nufile";
	print "$cmd\n";
	system($cmd);
    }
}
elsif ($shift > 0)
{
    for ($i = $#ARGV-1; $i >= 0 ; $i--)
    {
	($sn, $num, $ext) = split /\.+/ , $imagefiles[$i];
	$a = $num+$shift;
	$nufile = $sn.".".$a.".".$ext;
	$cmd = "mv ". $imagefiles[$i]." $nufile";
	print "$cmd\n";
	system($cmd);
    }
}