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#! /usr/bin/perl
use strict;
use warnings;
use Errno qw();
use Getopt::Long;
use Pod::Usage;
our $VERSION = '0.01';
my (
$opt_help, $opt_version, $opt_touch_file, $opt_ignore_case, $opt_match_str,
my $opt_span = 0;
my $opt_threshold = 1;
help => \$opt_help,
version => \$opt_version,
'file=s' => \$opt_touch_file,
'ignore-case' => \$opt_ignore_case,
'match=s' => \$opt_match_str,
'pipe' => \$opt_pipe,
'span=i' => \$opt_span,
'threshold=i' => \$opt_threshold,
) or pod2usage(1);
if ($opt_help) {
} elsif ($opt_version) {
print "$VERSION\n";
exit 0;
die "mandatory option: --file (-f) is missing\n"
unless defined $opt_touch_file;
die "mandatory option: --match (-m) is missing\n"
unless defined $opt_match_str;
# prepare compiled expr
my $match;
eval {
$match = $opt_ignore_case ? qr/$opt_match_str/i : qr/$opt_match_str/;
die $@ if $@;
# prepare output handle
my $fh;
if ($opt_pipe) {
die "no command\n"
unless @ARGV;
pipe my $rfh, $fh
or die "failed to create pipe:$!";
unless (my $pid = fork) {
die "fork failed:$!"
unless defined $pid;
# child process
close $fh;
open STDIN, '<&', $rfh
or die "failed to redirect piped input to stdin:$!";
exec @ARGV;
die "failed to execute:$ARGV[0]:$!";
} else {
die "too many arguments\n"
if @ARGV > 1;
if (@ARGV == 0 || $ARGV[0] eq '-') {
$fh = \*STDOUT;
} else {
open $fh, '>>', $ARGV[0]
or die "failed to open file:$ARGV[0]:$!";
# main loop
$| = 1;
my @match_at = map { 0 } (1 .. $opt_threshold);
while (my $l = <STDIN>) {
print $fh $l;
if ($l =~ /$match/) {
my $now = time;
shift @match_at;
push @match_at, $now;
if ($match_at[0] + $opt_span >= $now) {
utime undef, undef, $opt_touch_file or do {
if ($! == Errno::ENOENT) {
open my $fh, '>', $opt_touch_file
or die "failed to create file:$opt_touch_file:$!";
} else {
die "failed to touch file:$opt_touch_file:$!";
=head1 NAME
touch_if - touch another file if regexp matches, while writing STDIN to file
touch_if [options] out_file
touch_if [options] -p -- pipe_cmd pipe_args...
# common usage (in httpd.conf)
CustomLog "| touch_if -m ' 50[23] [^ ]+$' -f is_down access_log" common
=over 4
=item -f file_to_touch, --file=file_to_touch (mandatory)
file to be touched when a match (or matches) has been found
=item -m regexp, --match=regexp (mandatory)
regular expression to be applied against each line of input
=item -i, --ignore-case
ignore case
=item -p, --pipe
if not set, touch_if writes the input into out_file. If set, arguments are treated as a command to spawn to handle the input.
=item -s seconds, --span=seconds (default: 0)
=item -t count, --threshold=count (default: 1)
touches file if and only if the match has been found more than `count' times within `seconds' seconds
Touch_if is a script that writes input from STDIN to file, but while doing so, tests each line of the input against given regular expression, and if it matches, touches another file.
It is useful for detecting errors from log output. Other processes (like crontab tasks) should be used to check the last-modified date of the touched file and send alerts to administrators.
=head1 AUTHOR
Kazuho Oku