#!/bin/bash
#
# Runs a command in a screen session, or re-attaches to such a screen session if
# it already exists.
#

main () {
	force=0
	screen_id=""

	while getopts ":hvfi:" option; do
		case $option in
		h)
			usage 0
			;;
		v)
			echo "scrot - screen run (once)"
			echo "(C) 2006, Matthew Gates <matthew@porpoisehead.net>"
			echo "Distributed under the terms of the GNU GPL (v2)"
			exit 0
			;;
		f)
			force=1
			;;
		i)
			screen_id="$OPTARG"
			;;
		*)
			echo "ERROR: unknown option: $option" 2>&1
			;;
		esac
	done

	shift $(($OPTIND - 1))

	if [ $# -lt 1 ]; then
		usage 1
	fi

	if [ "$screen_id" = "" ]; then
		screen_id=scrot$1
	fi

	session=$(screen -ls  |grep \.$screen_id 2>&1)
	session_id=$(echo "$session" |awk '{ print $1 }')
	session_state=$(echo "$session" |awk '{ print $2 }')
	session_count=$(echo "$session" |grep -v '^ *$' |wc -l)

	case $session_count in
	0)
		start_prog $@
		;;
	1)
		try_reconnect $@
		;;
	*)
		multiple_sessions $@
		;;
	esac
}

start_prog () {
	echo "Starting new VLC session in screen"
        # sleep 1
	screen -S $screen_id $@
}

try_reconnect () {
	case "$session_state" in 
	\(Detached\))
		echo "$1 session is detached, re-attaching"
		# sleep 1
		screen -r $session_id
		;;
	\(Attached\))
		if [ $force -eq 1 ]; then
			echo "forcing dis-connection of other screen session..."
			pid=$(echo $session_id |cut -d . -f 1)
			kill -HUP $pid
			# sleep 1
			echo "attaching to session..."
                	screen -r $session_id
			exit 0
		else
			echo "Session is already attached to screen session $session_id"
			echo "Use -f option to force connection here."
		exit 1
		fi
		;;
	*)
    		echo "ERROR: no session found despite it looking like one!" 1>&2
		exit 127
    		;;
	esac
}

multiple_sessions () {
	echo "It seems id $1 is already running in more than one session..."
	echo "You should connect to one using \"screen -r [id]\" and kill it"
	screen -ls |grep \.$screen_id 2>&1
	exit 2
}

usage () {
	echo "Usage:"
	echo "    scrot [-f] [-i id] command ..."
	echo ""
	exit ${1:-0}
}

main $@

exit 0

__END__

=head1 NAME 

scrot - SCreen Run One Time

=head1 SYNOPSIS

scrot [options] program [args]

=head1 DESCRIPTION

scrot runs a program in a screen session one time only.  The first
time a program is run it starts a new session, subsequent calls to
scrot with the program name (or ID - see option B<-i>) connect the
calling terminal to the existing screen session.  This is useful if
you use a terminal based IRC client/mail client/audio player, and want
to take it over on the console when you X session needs to be
re-started, or you lose the terminal for whatever reason.

Each program is run with an ID which is the item which is kept unique.
By default the ID is the program name with no arguments, but can be
specified using the B<-i> option.

=head1 OPTIONS

=over

=item B<-f>

Force the current terminal to grab existing sessions.  Without this
option, if an existing session with the same ID exists the normal
behavior is to warn the user that one with the ID exists.  Using this
option will force scrot to take over the session.

=item B<-h>

Print the command line syntax an option details.

=item B<-i> I<id>

Specify the ID of the program to run.  If this option is not
specified, the program name will be used.

=item B<-v>

Print the program description and version.

=back

=head1 ENVIRONMENT

N/A

=head1 FILES

N/A

=head1 EXAMPLES

I use scrot to run the IRC client IRSSI.  I do this with the alias
irc, defined as follows (bash alias syntax):

 alias irc='scrot -f irssi'

This simply calls irssi (my IRC client) with scrot making sure there
is only one instance at any one time.  If there is an existing session
in another terminal, the B<-f> option forces disconnection from that
terminal.  This way I can switch IRC between console and xterm
sessions without having to quit IRC.  :)

=head1 LICENSE

scrot is released under the GNU GPL (version 2, June 1991).  A
copy of the license should have been provided in the distribution of
the software in a file called "LICENSE".  If you can't find this, then
try here: http://www.gnu.org/copyleft/gpl.html

=head1 AUTHOR

Matthew Gates <matthew@porpoisehead.net>

http://porpoisehead.net/

=head1 CHANGELOG

=over

=item Date:2006-06-01 Created, Author MNG

Original version.

=item Date:2006-08-22 Documented, MNG

Added this cruft.

=back

=head1 BUGS

Please report bugs to the author.

=head1 SEE ALSO

screen(1).

=cut