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();