Places pre/post hooks for application restarting while in lock mode. Designed for i3 window manager, but could be used for others as well.

i3lock.sh

#!/bin/bash
###############################################################################
#
# file:     i3lock.sh
#
# Purpose:  manages i3lock with pre/post application restart hooks.
#           eg. kills skype/pidgin once locked is triggered, and opens them
#               again once lock is released.
#
# Usage:    set call to this script in i3 config file, eg:
#
#               # lock (traditional Ctrl+Alt+L)
#               bindsym Control+mod1+l exec --no-startup-id ~/.i3/i3lock.sh
#
###############################################################################
#
# Copyright 2013 Bruno Braga
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
#
###############################################################################
#
# Developer Notes: For troubleshooting this, use an output redirection wrapper.
#
###############################################################################


# ############################
# CONFIGURABLE SETTINGS: BEGIN
# ############################

#
# write here (space separated within single quotes) all applications that must
# be killed and restarted upon lock triggering. For this to work properly, make
# sure the names registered here are accessible in your $PATH.
#
managed_apps='skype eclipse'

#
# Place here what is the lock command to be executed between pre/post hooks
# (this was left here intentionally to serve different tastes of i3lock).
#
lock_cmd='i3lock -n -c 000000'

# ############################
# CONFIGURABLE SETTINGS: END
# ############################

# No need to change anything beyond this point!

# ##########################
# Helper functions
# ###########################

#
# Kills a PID gracefully, or forcefully if not successful within
# 10 sec, or ultimately leave if not completed in 30 sec.
#
function kill_pid() {
    pid=$1
    max_wait=10 # seconds
    max_overall_wait=30 # seconds
    count=1
    while [ `ps -p $pid --no-headers | wc -l` -eq 1 ]; do
        count=$(expr $count + 1)
        if [ $count -gt $max_overall_wait ]; then
            break # could not kill, leave!
        else

            if [ $count -gt $max_wait ]; then
                kill -9 $pid # taking too long, issue a SIGKILL
            else
                kill $pid # try to kill gracefully
            fi
            sleep 1
        fi
    done
}

#
# Retrieve available PID(s) of an application
#
function get_pids() {
    what=$1
    ps -ef | grep $what | grep -v grep | awk 'BEGIN { FS=" " } { print $2; }'
}

#
# Starts an application if not already running
#
function start_app() {
    what=$1
    pids=`get_pids $what`
    if [ "$pids" == "" ]; then
        $what &
        logger -t $script_name "Started $what."
    fi
}

#
# Stops an application (including all of its PID(s)), if applicable.
#
function stop_app() {
    what=$1
    pids=`get_pids $what`
    if [ ! "$pids" == "" ]; then
        for pid in $pids; do # handle multiple entries, if applicable
            kill_pid $pid
        done
        logger -t $script_name "Stopped $what."
    fi
}

# ########################
# Main Hook Functions
# ########################

function prehook() {
    for app in $managed_apps; do
        stop_app $app
    done
    logger -t $script_name-prehook 'Executed.'
}

function posthook() {
     for app in $managed_apps; do
        start_app $app
    done
    logger -t $script_name-posthook 'Executed.'
}

# #########
# Main Code
# #########

# Just used to register the tag in syslog, for troubleshooting
script_name=`basename $0 .sh`

logger -t $script_name 'Starting script'
prehook
$lock_cmd
posthook
logger -t $script_name 'Finished script'

# Done!