#!/bin/bash

# record-stream v1.2
#
# Make program recordings from an online (usually MP3-type) stream.
#
# Requires find(1), pgrep(1), ps(1) with -o for display formatting,
# mktemp(1), and wget.
#
# Run this script from cron (or your favorite command scheduler) as often
# as you want the files to be divided up. For example, if you want hour-long
# files, run this script hourly:
#
# @reboot         /usr/local/bin/record-stream
# 0 * * * *       /usr/local/bin/record-stream
#
# The @reboot line is supported by Vixie cron to make sure that program
# recordings are re-started immediately upon reboot instead of waiting for
# the next top of the hour.
#
#
# High-level overview:
#
# At each run:
# - Old files are removed from $ROOT according to the retention period
#   specified by $KEEPDAYS.
# - The stream starts recording from $URL to /tmp/ (or TMPDIR, if set in
#   the environment)
# - The stream is given a few seconds to ensure it has started successfully.
# - If the stream has started recording successfully, the previous
#   instance is signaled to shut down its recording and move the file
#   into place as $ROOT/$FILE.
#
#
# Copyright (c) 2005-7, John Morrissey
# 
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 2 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc., 59
# Temple Place, Suite 330, Boston, MA 02111-1307, USA.

URL=http://your/stream
ROOT=/path/to/recordings/
FILE=recording-$(date +%Y-%b-%d-%H%M | tr A-Z a-z).mp3
KEEPDAYS=31

# Keep $KEEPDAYS calendar days' worth of recordings
find $ROOT -maxdepth 1 -daystart -mtime +$KEEPDAYS -name \*.mp3 -exec rm {} \;

if ! temp_out=$(mktemp -qt record-aircheck.XXXXXX); then
	echo "Can't create tempfile, aborting."
	exit 1
fi

stop_wget() {
	# Disown our wget child first; otherwise, bash(1) will emit:
	#   [1]+  Terminated              wget
	# which there is no way to silence.
	disown %?wget
	for wget_pid in $(pgrep -f "wget --output-document=/tmp/record-aircheck\.[[:alnum:]]{6} --quiet $URL"); do
		# Make sure it's our child.
		if [ "$(ps -o ppid= $wget_pid)" == $$ ]; then
			kill $wget_pid
			break
		fi
	done
}
trap stop_wget SIGUSR1

set -m
wget --output-document=$temp_out --quiet $URL &
# Give it time to start and connect; if something isn't going to work, it's
# probably going to break in the first couple of seconds.
sleep 5
if [ $(jobs | wc -l) -lt 1 ]; then
	echo "Couldn't start recording stream, aborting."
	exit 1
fi

# Signal any past invocations to stop their wget children; otherwise,
# they'll keep recording indefinitely.
for wget_pid in $(pgrep -f "wget --output-document=/tmp/record-aircheck\.[[:alnum:]]{6} --quiet $URL"); do
	wget_ppid=$(ps -o ppid= $wget_pid)
	if [ "$wget_ppid" -eq $$ ]; then
		# Don't commit suicide; this is the wget(1) we just started.
		continue
	fi
	# For some reason, previous instances of this script die (go
	# defunct), and I can't figure out why. Kludge around this by
	# checking to see if wget has been given init(8) as a parent,
	# and kill wget itself if so.
	if [ $wget_ppid == 1 ]; then
		kill $wget_pid
	else
		kill -USR1 $wget_ppid
	fi
done

# Wait until the next invocation signals us to terminate our wget(1), then
# move the recording into place.
wait
mv -f $temp_out $ROOT/$FILE
chmod 644 $ROOT/$FILE