#!/usr/bin/perl

# Die screaming instead of silently if child fails
$SIG{PIPE} = sub { die("SIGPIPE"); };

# $block is the read size, 1 meg is probably OK.
# $chunk is the output size.  With a chunk of 2 and block of 1024*1024,
# it writes 2 meg files.
my $block=1024*1024, $chunk=2;

my $running=1, $ccount=0, @l=@ARGV;

while($running) {
        my $n, $fname=sprintf("%08d", $ccount++);
        my $fr=\$fname;

        # Use given arguments as a command, with @FNAME@ substituted
        # for an incrementing number like 00000001
        open(OUT, "|-",
                map { my $v=$_; $v =~ s/\@FNAME\@/${$fr}/; $v } @l
        );

        for($n=0; $n<$chunk; $n++)
        {
                my $bytes=read(STDIN, $data, $block);
                defined($bytes) || die ("Error reading STDIN");
                if($bytes < 1) { # Ran out of data, stop reading
                        $running=0;
                        last;
                }

                print OUT $data;
        }

        close(OUT);
}

printf(STDERR "Wrote %d chunks of %d bytes\n", $ccount, $block*$chunk);

$ chmod +x pipesplit.pl
$ tar cvzf - /backup | openssl aes-256-cbc -salt -k "password" |
        ./pipesplit.pl curl -u user:pass ftp://hostname/path/@FNAME@ -T -

100 2048k    0     0    0 2048k      0  8368k --:--:-- --:--:-- --:--:-- 8393k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 2048k    0     0    0 2048k      0  8367k --:--:-- --:--:-- --:--:-- 8393k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 2048k    0     0    0 2048k      0  8335k --:--:-- --:--:-- --:--:-- 8325k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
...
                                 Dload  Upload   Total   Spent    Left  Speed
100 2048k    0     0    0 2048k      0  8389k --:--:-- --:--:-- --:--:-- 8427k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100     5    0     0    0     5      0     21 --:--:-- --:--:-- --:--:--    21
Wrote 17 chunks of 2097152 bytes

$