# This is TAC
# reverse of cat
#
# Take a list of files as command line parameters
# and display the files on STDOUT
# last file first
# displaying each file backwards

# The files are concatenated in 'normal' order to a temporary file
# which is then read and displayed in reverse

# check the number of parameters..


my $argCount = $#ARGV+1;
if ($argCount<2)
	{
	exit 0;
	}
# open the temporary file
use Fcntl;
use POSIX;
my $outputFile;
do {
    $outputFile = tmpnam();
} until sysopen(OUTPUTFILE, $outputFile, O_RDWR|O_CREAT|O_EXCL, 0666);


# for every file..
while (@ARGV)
	{
	# open it

	my $fileName = shift;
	open ( MYFILE, " $fileName" ) or die "Cant open file $fileName";
	# and write each line to the temporary file..

	foreach (<MYFILE>)
		{ print  OUTPUTFILE $_; }
	close MYFILE;
	print OUTPUTFILE "\n";
	print "Done $fileName -\n";
	}
close OUTPUTFILE;

# now read it in backwards..
my $inputFile = $outputFile;
open ( INPUTFILE, "< $inputFile");
my $char;
my $fromEnd=1; 
my $fileSize = (stat INPUTFILE)[7];
# we seek to a position a distance from the end, and read a single character
# the distance from end increases till we hit the start
while ($fromEnd<$fileSize+1)
	{
	seek INPUTFILE, -$fromEnd, 2; # last char
	read INPUTFILE, $char, 1;
	print $char;
	++$fromEnd;
	}


close INPUTFILE;
unlink $inputFile;