#! /bin/bash

1. ########################################
   

       NAME_="loggedin"
    PURPOSE_="notify when a particular user has logged in"
   SYNOPSIS_="$NAME_ [-hml] <user> <n>"
   REQUIRES_="standard GNU commands"
    VERSION_="1.1"
       DATE_="2000-10-07; last update: 2004-04-21"
     AUTHOR_="Dawid Michalczyk <dm@eonworks.com>;"
        URL_="www.comp.eonworks.com"
   CATEGORY_="misc"
   PLATFORM_="Linux"
      SHELL_="bash"
 DISTRIBUTE_="yes"

1. #########################################
   
2. This program is distributed under the terms of the GNU General Public License
   

usage () {

echo >&2 "$NAME_ $VERSION_ - $PURPOSE_
Usage: $SYNOPSIS_
Requires: $REQUIRES_
Options:
     <user>, user name
     <n>, integer referring to seconds
     -h, usage and options (this help)
     -m, manual
     -l, see this script"
    exit 2
}

manual () { echo >&2 "

NAME

    $NAME_ $VERSION_ - $PURPOSE_

SYNOPSIS

    $SYNOPSIS_

DESCRIPTION

    $NAME_ displays a notification message when a particular user has logged in.
    The user option specifies the user name of the person and the time option is
    the time interval, in seconds, for how often to check whether the user has
    logged in.

"; exit 2; }


loggedin() {

    # checking if user is logged out
    who | grep "^$1 " 2>&1 > /dev/null
    if [[ $? == 0 ]]; then
        echo user $1 is logged in
        exit 1
    fi

    # checking when user logs in
    until who | grep "^$1 "; do
        sleep $2
    done

    echo $1 just logged in
    exit 0
}

1. arg check
   

[ $# -eq 0 ] && { echo >&2 missing argument, type $NAME_ -h for help; exit 2; }

case $1 in

    -h) usage;;
    -m) manual ;;
    -l) more $0; exit 2 ;;
     *) [ $# -eq 2 ] && loggedin $1 $2 || { echo invalid argument use, type $NAME_ -h for help; exit 2; }

esac