#! /bin/bash
# #############################################################################

       NAME_="lowstorage"
    PURPOSE_="notify when space on any storage device is less then n Megabytes"
   SYNOPSIS_="$NAME_ [-hl] <n> [device..]"
   REQUIRES_="standard GNU commands, xmessage"
    VERSION_="1.4"
       DATE_="1999-08-10; last update: 2004-12-09"
     AUTHOR_="Dawid Michalczyk <dm@eonworks.com>"
        URL_="www.comp.eonworks.com"
   CATEGORY_="admin"
   PLATFORM_="Linux"
      SHELL_="bash"
 DISTRIBUTE_="yes"

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

usage () {

echo >&2 "$NAME_ $VERSION_ - $PURPOSE_
Usage: $SYNOPSIS_
Requires: $REQUIRES_
Options:
     <n>, an integer referring to Mb
     [device], full path to the device(s) to exclude, eg: /dev/cdrom
     -h, usage and options (this help)
     -l, see this script"
    exit 2
}

# tmp file set up
tmp_1=/tmp/tmp.${RANDOM}$$
tmp_2=/tmp/tmp.${RANDOM}$$
tmp_3=/tmp/tmp.${RANDOM}$$

# signal trapping and tmp file removal
trap 'rm -f $tmp_1 $tmp_2 $tmp_3 >/dev/null 2>&1' 0
trap "exit 2" 1 2 3 15

# enabling extended globbing
shopt -s extglob 

# option handling
case $1 in
    -h) usage ;;
    -l) more $0; exit 2 ;;
    +([0-9])) # arg1 can only be an integer

    mb=$1
    shift
    while :;do

        if [[ $@ ]];then
            df -m | sed '1d' > $tmp_1
            for a in $@;do
                echo $a | sed 's-\/-\\/-g' >> $tmp_2
            done
            sed -e 's-^-/-g' -e 's-$-/d-' $tmp_2 > $tmp_3
            sed -f $tmp_3 $tmp_1 > $tmp_2
        else
            df -m | sed '1d' > $tmp_2
        fi

        while read dev blocks used free perc mounted;do

            if (( $free < $mb ));then

                # display windowed message if x is running; ring a bell
                ps -aux | grep -q xinit
                if [ $? = 0 ];then
                    echo -en \\a
                    xmessage -center Device $dev mounted on \
                    $mounted is running low on space! Only ${free}Mb left.
                    exit 0
                else
                    # write message to terminal and ring a bell
                    echo -e \\a Device $dev mounted on $mounted is running \
                    low on space! Only ${free}Mb left.
                    exit 0
                fi
            fi


        done < $tmp_2
        
        rm -f $tmp_2    
        sleep 60s # how often to check disk

    done ;;

    *) echo invalid argument, type $NAME_ -h for help ; exit 2 ;;

esac