scripts/thinkpad/kbd_backlight.pl

#!/usr/bin/perl

use strict;
use warnings;

our $maxfile = "/sys/class/leds/tpacpi\:\:kbd_backlight/max_brightness";
our $current = "/sys/class/leds/tpacpi\:\:kbd_backlight/brightness";
our $sleepfile = "$ENV{HOME}/.spool/kbd_sleep";

sub readFile
{
        my $file = shift;
        my $ret;
        if (open(my $fh, '<', $file)) {
                $ret = readline($fh);
                chomp $ret;
                close($fh);
        } else {
                die "Failed to read $file: $?\n";
        }
        return $ret;
}


sub writeFile
{
        my ($file, $value) = @_;
        if (open(my $fh, '>', $file)) {
                print $fh $value;
                close($fh);
        } else {
                die "Failed to write $current\n";
        }
}

sub sleepFile
{
        my $now = readFile($current);
        writeFile($sleepfile,$now);
        writeFile($current,0);
}

sub restoreFile
{
        unless (-e $sleepfile) {
                die "Missing '$sleepfile'. Must not have slept prior to restore.\n"
        }
        my $value = readFile($sleepfile);
        writeFile($current,$value);
        unlink($sleepfile);
}

sub rotateFile
{
        my $max = readFile($maxfile);
        my $now = readFile($current);
        my $new = (($now+1) % ($max+1));
        writeFile($current,$new);
}

if (defined($ARGV[0])) {
        if ($ARGV[0] eq 'sleep') {
                sleepFile();
                exit(0);
        } elsif ($ARGV[0] eq 'restore') {
                restoreFile();
                exit(0);
        } elsif ($ARGV[0] ne 'rotate') {
                die "Invalid mode '".$ARGV[0]."'. 'rotate', 'sleep', or 'restore'\n";
        }
}

rotateFile();