help with bourne shell script

Shell Programming and Scripting
1

Attempting to write a script to eventually notify me via email for when there is packetloss across the backbone. I am looking for values greater than 0% in the mtr field.

#!/bin/sh
target=www.google.com
date +"%D"_"%T" >> /home/rich/mtr.log
echo "----------------------------------------" >> /home/rich/mtr.log
mtr -report -c 5 $target >> /home/rich/mtr.log
mtrlog=`cat /home/rich/mtr.log | awk '/%/ { print $2 }'`
zeroloss=0%
if [ "$mtrlog" = "$zeroloss" ] ; then
        echo "No packetloss"
fi

With what I have above, it's echoing more than one 0% for the mtr field ( obiously) and comparing it to the zeroloss of 0% which results in it not echoing no packetloss. Do I need a for loop in there for each line?

Example when stripping script to just variables it comes up with:

mtrlog 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0%

zeroloss 0%
2

I'm not familiar with the 'mtr' command, but I'll guess that its sending out pings and presenting a summary that includes packet loss. Your getting tripped up because you are parsing the whole log file and not just the last mtr output.

I'd write the script just a bit differently; piping all of the mtr output straight to awk and letting it do all of the work.

#!/usr/bin/env sh
target=www.google.com
log=/home/rich/mtr.log
date +"%D"_"%T" >>$log

mtr -report -c 5 $target | awk -v logf=$log '
   { print >>logf; }          # save all mtr output to log file for history
   index( $2, "%" ) > 0  {  # you could do /%/ but that might catch more than youd like  /packet loss/ would be best if that is in the output
        if( max < $2+0 )     # allow for multiple in output; keep largest
             max = $2+0;     # +0 forces it to be numeric
   }
   END { 
      if( max == 0 )          # write to tty the findings of this pass
           printf( "no packet loss\n" );
      else
           printf( "packet loss of %d%%\n", max );
   }'

I'd also use Kshell or bash over sh, unless for some reason you're required to use sh. #!/usr/bin/env ksh at the top should be all you need to switch.

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