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I have multiple servers and want to set up a periodic check so that trapserver(s) has correct trapaddress(es). trapserver 1 as 10.10.10.1 and trapserver2 as 10.10.10.2. However the below script does not see $trapaddress value of 10.10.10.x with "10.10.10.x" as equal?

Not sure where I am going wrong?

Many thanks

#!/bin/bash
for LINE in $( cat /home/username/serverslist.txt )
do
SERVER=`(echo $LINE | awk -F : '{ print $1 }')`

echo " "

echo $SERVER
traphost=$( ssh $SERVER -t sudo cat /etc/traphost.txt )
trapaddress=$( ssh $SERVER -t sudo cat /etc/trapaddress.txt )
echo -e " Traphost is $traphost \n Trapaddress is $trapaddress"

if [ $traphost = "trapserver1" ] && [ $trapaddress= "10.10.10.1" ] || [ $traphost = "trapserver2" ] && [ $trapaddress= "10.10.10.2" ] ;
       then
        echo "server is happy."
       else
        echo  " $servername server has incorrect $trapaddress ."
fi
done
ilkkachu
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Syed Mazhar
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  • There are lots of things to comment here on but, taking just one, add a space before `=` in the tests. In other words, replace `[ $trapaddress= "10.10.10.1" ]` with `[ "$trapaddress" = "10.10.10.1" ]` – John1024 Feb 19 '19 at 21:50
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    Also, in general, whenever you have a shell script error, a good first step is to cut and paste your code into [shellcheck.net](http://www.shellcheck.net/) and correct the errors (important) and warnings (might be important) that it identifies. If you have trouble understanding its messages, then come here and ask. – John1024 Feb 19 '19 at 21:51

1 Answers1

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First, I assume the lack of space before the = in [ $trapaddress= "10.10.10.1" ] is a typo. If it weren't you'd immediately get an error from [.

Second, you have a problem in the relation between the && and || operators. In the shell, they are processed left to right, so your condition doesn't do what you want it to do. In fact, this:

if cond1 && cond2 || cond3 && cond4; then ...

is more like this:

if ((cond1 && cond2) || cond3) && cond4; then ...

Notably, it requires cond4 to be true. What you want is either

if ( ... && ...) || ( ... && ... ); then ...

or 

if [[ ... && ... || ... && ... ]]; then ...

(Within [[ .. ]] they do have the usual relative precedence.)

If you want, you could concatenate the variables to make the comparison easier, assuming they never contain e.g. a slash:

if [[ "$traphost/$trapaddress" = "trapserver1/10.10.10.1" ||
      "$traphost/$trapaddress" = "trapserver2/10.10.10.2" ]]; then ...

Note that you want to quote the variables to avoid word splitting, see When is double-quoting necessary?

ilkkachu
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  • I have changed to this however I am experiencing the same issue. The problem is that although the value of $trapaddress echoing as 10.10.10.1 but if condition does not match it with "10.10.10.1", which is really strange and goes to else condition, instead of then. if [[ "$traphost/$trapaddress" = "trapserver1*/10.10.10.1" || "$traphost/$trapaddress" = "trapserver2*/10.10.10.2" ]]; then ... – Syed Mazhar Feb 19 '19 at 22:25
  • @SyedMazhar, ah, right. Check that you don't have any traiiling whitespace or such in there. Put something like `printf "host <%s> addr <%s>\n" "$traphost" "$trapaddress"` there in the script to see that. Or even look at the file itself to see any invisible characters. `od -c /etc/trapaddress.txt` or such should do. If there's anything to see [edit your question](https://unix.stackexchange.com/posts/501709/edit) to add it in, the comments don't really lend well for presenting code and output like that – ilkkachu Feb 19 '19 at 22:26
  • True, there seems to be issue with line 1 changed.. is there a way I can transfer $IP value without just the IP address and remove any whitespaces? will look further. thanks output was 1c1 < 10.10.10.1 --- > 10.10.10.1 – Syed Mazhar Feb 19 '19 at 22:38
  • @SyedMazhar, there are probably better ways, but you already have used `awk`, so you could use it here, too. `awk '{ print $1 }' /etc/trapaddress.txt` would print just the first field, removing extra whitespace. Or `tr -dc '0-9.' /etc/trapaddress.txt`, it would remove anything but digits and dots. – ilkkachu Feb 19 '19 at 22:45
  • tr -dc '0-9.' worked perfectly , you are a star. Many thanks Sir. awk '{print $3 }' | tr -dc '0-9.' – Syed Mazhar Feb 19 '19 at 22:56