:
##########################################################################
# Title      :	einlog - keep a log file of login and logout time stamps
# Author     :	Heiner Steven <heiner.steven@odn.de>
# Date       :	1993-12-10
# Requires   :	
# Category   :	Desktop
# SCCS-Id.   :	@(#) einlog	1.9 05/08/29
##########################################################################
# Description
#	Keep a log file of the first and the last login
# See also
#	logstat
##########################################################################

PN=`basename "$0"`			# Program name
VER='1.9'

: ${LOGFILE:=$HOME/lib/log}
: ${TMPDAT:=/tmp/log.$$}
lock=$LOGFILE.lock

DateForm='%Y-%m-%d %H:%M (%a)'
Date=`LANG=C date '+%Y-%m-%d'`
currenttime=`LANG=C date "+$DateForm"`

usage () {
    echo >&2 "$PN - keep a log file of login and logout time stamps, $VER
usage: $PN {-i | -o}
    -i:	log in
    -o: log out

Log file:
    $LOGFILE"
    exit 1
}

msg () {
    for msgLine
    do echo "$PN: $msgLine" >&2
    done
}

fatal () { msg "$@"; exit 1; }

set -- `getopt :haeio "$@" || exit 1` || usage
[ $# -lt 1 ] && usage			# "getopt" detected an error

Mode=login				# {login|logout}
while [ "$#" -gt 0 ]
do
    case "$1" in
	-i|-e)	Mode=login;;
	-o|-a)	Mode=logout;;
	--)	shift; break;;
	-h)	usage;;
	-*)	usage;;
	*)	break;;			# First file name
    esac
    shift
done

# System V date command preferred
PATH="/usr/5bin:$PATH"	export PATH

if mkdir "$lock" >/dev/null 2>&1
then
    # Aquired lock. Remove it when the program terminates, or after
    # reception of a signal.

    trap 'rmdir "$lock" >/dev/null 2>&1' 0
    trap "exit 2" 1 2 3 13 15
else
    fatal "could not create lock: $lock"
fi

if [ -f "$LOGFILE" ]
then
    :
else
    cat <<-! > "$LOGFILE"
	# log - login and logout times (first and last login)
	# created `date +"$DateForm"`

	!
    chmod 600 "$LOGFILE"
fi

# Only one entry per day. Always add an "EIN" entry if it does not exist
# already.

grep "EIN: $Date" < "$LOGFILE" > /dev/null || 
  echo "EIN: $currenttime
AUS: $currenttime" >> "$LOGFILE"

case "$Mode" in
    login)
	# "EIN" record was already written.
	;;

    logout)
    	# Keep file time stamp by copying it using "cp -p"
	cp -p "$LOGFILE" "$TMPDAT" ||
		fatal "cannot create temporary file: $TMPDAT"
	{ 
	    grep -v "AUS:.* $Date" < "$LOGFILE" 	# once per day
	    echo "AUS: $currenttime"
	} > "$TMPDAT" &&
	    mv -f "$TMPDAT" "$LOGFILE"
	;;

    *)
    	usage
	;;
esac