slowcat10

#!/usr/bin/perl
## Print input lines with a small delay (0.1s) bursts of 20, interactive.
#
# Usage tip: find . -name 'mask' | shuf | xargs --open-tty slowcat10
# q     - quit
# space - pause/unpause
# a     - list remaining files (arguments)
# n     - go to next file
# f     - print filename

use Term::ANSIColor;
use Term::ReadKey;

ReadMode 4; # raw

my $burst = 20;
my $delay = 5;
my $left = $burst;
my $lastdelay = 0;
my $announcefile = 1;
my $key;

$|++;
while (($_=<>) ne '') {
	if ($announcefile) {
		print colored("File: $ARGV", "green");
		print color("reset");
		print("\n");
		$announcefile = 0;
	}
	# Preserve remaining delay between loops
	if ($lastdelay == 0) {
		print colored(sprintf("%3d", $.), "dark white");
		print color("reset");
		print colored("  " . $_, "bold white");
		print color("reset");
		select(undef, undef, undef, 0.01);
	}
	$key = ReadKey(-1);
	if (defined $key) {
		# Go handle the key
	} elsif (--$left <= 0) {
		# Low latency
		my $multiplier = 4;
		$lastdelay = $delay * $multiplier;
		# Set before the loop so the rest of the delay is preserved for
		# the next main loop
		$left = $burst;
		while (--$lastdelay > 0) {
			$key = ReadKey(-1);
			last if (defined $key);
			select(undef, undef, undef, 1/$multiplier);
		}
	}
	if (defined $key) {
		if ($key eq ' ') {
			print colored("Paused, press Space to continue or 'q' to quit", "green");
			print color("reset");
			print("\n");
			while ($key ne 'q') {
				$key = ReadKey(-1);
				if (defined $key) {
					if ($key eq ' ') {
						# Print the next burst
						$lastdelay = 0;
						last;
					}
					last if ($key eq 'q');
				}
				select(undef, undef, undef, 1/3);
			}
		}

		if ($key eq 'q') {
			print colored("Bye", "green");
			print color("reset");
			# Colored newline leaves colored cursor
			print("\n");
			last;
		}

		if ($key eq 'f') {
			print colored("File: $ARGV", "green");
			print color("reset");
			print("\n");
		}

		if ($key eq 'n') {
			print colored("Go to next file (current: $ARGV)", "green");
			print color("reset");
			print("\n");
			close ARGV;
			$announcefile = 1;
			$lastdelay = 0;
		}

		if ($key eq 'a') {
			print colored("ARGV: @ARGV", "green");
			print color("reset");
			print("\n");
		}
	}
}

END {
	ReadMode 0;
}