srbug

#!/bin/sh
# -*- tab-width:  4 -*- ;; Emacs
# vi: set tabstop=4     :: Vi/ViM
############################################################ INFORMATION
#
# A simple script to launch a sub-shell in the background that continually
# updates the sudo(8) (or other sr-like utility) timestamp to prevent timeout.
#
# This is most useful if you know that you're going to need to execute many
# commands but spread-out over a sizable time period but want to prevent the
# requirement to enter your password every time.
#
# After launching this program, there should be a backgrounded process visible
# by standard job-control utilities (such as `jobs'). When you exit your shell
# this job will be terminated (unless configured otherwise in your shell
# configuration).
#
# Usage (requires sh or bash):
#   . path/to/srbug
#
############################################################ CONFIGURATION

#
# How long to sleep in-between executions
#
SLEEP_SECONDS=10

#
# Maximum duration to run (in seconds).
# Set to zero to disable (not recommended).
#
TIME_LIMIT=9000 # 2.5 hours

############################################################ GLOBALS

#
# Global exit status variables
#
SUCCESS=0
FAILURE=1

#
# Standard utility pathnames
#
SR=sudo
SLEEP=sleep

############################################################ MAIN SOURCE

#
# Execute once before launching the background process (in case we are
# presented with a password prompt).
#
$SR -v || exit $FAILURE

#
# Launch a sub-shell in the background
#
(
    n=0
    while [ $n -le $TIME_LIMIT -o $TIME_LIMIT -eq 0 ]; do
        #
        # Exit if we lost our controlling TTY
        #
        tty=$( ps -p$! -otty= 2> /dev/null )
        case "$tty" in
        *ty*|*ts*) : do nothing;;
        *) exit $FAILURE;;
        esac

        $SLEEP 1

        [ $(( $n % $SLEEP_SECONDS )) -eq 0 ] && $SR -v
        n=$(( $n + 1 ))
    done
) &

#
# Inform the user of what we did
#
echo "Backgrounded process $!"

################################################################################
# END
################################################################################
#
# $Header$
#
# $Copyright: 2011 Devin Teske. All rights reserved. $
#
# $Log$
#
################################################################################