#!/usr/bin/perl -w
use strict;					# Don't allow any funny stuff. Perl is confusing enough without it.
use Cwd; 

# bu2: incremental backup script

# This script will create a list of files to incrementally back up, based on a backup list normally used for full
# backups. Dates of each file found in the backup list is compared with the date of the last full backup, to
# determine whether it should be included. The name of the incremental backup filelist can be specified, or a
# default filename can be used.

if ($ENV{HOME} eq "/home/Peter") {				# I always back up from home directory,
  chdir("/home/Peter");						# so go there, because
}								# tar paths will be relative to home.
my $base = cwd();						# $base will have current working directory.
my $currentfile;						# holds current file to examine
my $bu2_mtime;							# Process any command line parameters

sub backuplist {						# Subroutine called check files & directories
  my $currentfile = shift;					# file or subdirectory to check, relative to $base
  my $tempdir = $base . "/" . $currentfile;			# full path from root to current file or directory
  my $nextdir;							# for next path level, if needed
  my $entry;							# an entry from the list
								# here, check whether it's a directory or not.
  if (-d $tempdir) {						# continue here only if looking at a directory
    chdir ($tempdir) || die "I can't get to $tempdir\n$!";	# report any error changing directory
    my @backuplist = <*>;					# get all directory entries to an array
    foreach (@backuplist) {					# go through the list and check for valid files
      $entry = $_;						# get an entry in the list
      next if (-l $entry);					# ignore links
      if (-d $entry) {						# if the entry is a directory,
        $nextdir = $currentfile . "/" . $entry;			# $nexdir will simulate current address off of $base
        &backuplist($nextdir);					# go check this directory
        chdir ($tempdir) || die "I can't return to $tempdir\n";	# this gets me back to where I was.
      } else {							# otherwise it's a file so check it.
      if ((-M $entry) < $bu2_mtime) {				# if the file was modified after this script...
         print OUT $currentfile . "/" . $entry,"\n";		# put the file and relative path into backup list
        }
      }
    }
  } else {							# end up here if it's a file, not a directory.
    if ((-M $tempdir) < $bu2_mtime) {				# check age of file relative to last full backup
      print OUT $currentfile,"\n";				# put the file into backup list
    }
  }
}

# process any command line arguments when this script is called.
my $infile = shift(@ARGV);					# declare some variables and
my $outfile = shift(@ARGV);					# pick up any command line arguments
my $tarfilename = shift(@ARGV);
if (not defined($infile)) {					# set defaults if none were provided
  $infile = "bin/backuplist";					# modify defaults for your own use
}
if (not defined($outfile)) {
  $outfile = "bin/incbackuplist";
}
if (not defined($tarfilename)) {
  $tarfilename = "incbackup";
}

if (not($infile =~ /^\//)) {					# if path isn't absolute, make it absolute!
  $infile = $base . "/" . $infile;				# prepend current working directory to input filename
}
if (not($outfile =~ /^\//)) {					# if path isn't absolute, make it absolute!
  $outfile = $base . "/" . $outfile;				# prepend current working directory to output filename
}
print "input file is ",$infile,"\n";				# confirm file names
print "output file is ",$outfile,"\n";				# 

open(OUT, ">$outfile");						# Open the output file for writing
open(IN, "<$infile");						# open the intput file for reading

$bu2_mtime = `which bu2`;					# Get path to this script
chomp($bu2_mtime);						# get rid of the newline...
$bu2_mtime = (-M $bu2_mtime);					# Get the date (mtime) of last full backup
print "Last full backup was done ",$bu2_mtime," days ago.\n";	# Report number of days since this script last modified.

while (<IN>) {							# While there are lines left to read,
  $currentfile = $_;						# Read in lines from the backup file list
  chomp($currentfile);						# lop off that newline
  &backuplist($currentfile);					# go check the file or directory for backing up
}

close(IN) || die "Can't close input file!\n";			# close the file I read in.
close(OUT) || die "Can't close output file!\n";			# close the file I created.

chdir $base || die "I can't get to $base\n$!";			# make sure we end up at the current working directory.	
print "Review $outfile to see which files will be backed up.\n";#
system "backmeup",$tarfilename,$outfile,"inc";			# invoke tar and create the backup.