CODEWITHSUNDEEP
bashshell
t3kg33k
t3kg33k

Reputation: 51

Bash shell script not working

I have a script I am trying to work out to scan my LAN and send me notification if there is a new MAC address that does not appear in my master list. I believe my variables may be messed up. This is what I have:

#!/bin/bash

LIST=$HOME/maclist.log
MASTERFILE=$HOME/master
FILEDIFF="$(diff $LIST $MASTERFILE)"

# backup the maclist first
if [ -f $LIST ]; then
       cp $LIST maclist_`date +%Y%m%H%M`.log.bk
else
        touch $LIST
fi 

# this will scan the network and extract the IP and MAC address
nmap -n -sP 192.168.122.0/24 | awk '/^Nmap scan/{IP=$5};/^MAC/{print IP,$3};{next}' > $LIST

# this will use a diff command to compare the maclist created above and master list of known good devices on the LAN
if [ $FILEDIFF ] 2> /dev/null; then
        echo
        echo "---- All is well on `date` ----" >> macscan.log
        echo
else
       # echo -e "\nWARNING!!" | `mutt -e 'my_hdr From:[email protected]' -s "WARNIG!! NEW DEVICE ON THE LAN" -i maclist.log [email protected]`
        echo "emailing you"
fi

When I execute this when the maclist.log does not exist I get this response:

diff: /root/maclist.log: No such file or directory

If I execute it again with the maclist.log file existing the file gets renamed from the cp line without any issue.

Upvotes: 0

Views: 48

Answers (1)

psmears
psmears

Reputation: 28110

The line

FILEDIFF="$(diff $LIST $MASTERFILE)"

executes the diff when it is run (not when you use $FILELIST later). At that time the list file hasn't been created.

The easiest fix is just to put the diff command in full where $FILELIST is currently used.

Upvotes: 1

Related Questions