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Compare an item in one line of a file against an item in the next line of the same file


 
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# 1  
Old 04-17-2020
Compare an item in one line of a file against an item in the next line of the same file

Hi all,

I found the following old thread very useful and in particular the very helpful post by @frans
Code:
while read A # read line and put in variable A. If unreadable (EOF) the break the loop.
do
    read B # read next line and put in variable B
    ((i+=2)) # increment variable i by 2 (like i=i+2)
    # [ "$A" != "$B" ] && echo "Lines $((i-1)) and $i are different"
    # can be written
    if [ "$A" != "$B" ] # if values of variables A and B are different ('[ ]' stands for 'test')
    then echo "Lines $((i-1)) and $i are different" # OK ?
    fi
done < inputfile # tells the loop to read from inputfile (else, it would read from keyboard.)

However, I am looking to try and compare one item / word from the first line to see if that same item is part of the second line

So in a sense, I'm trying to say something like
if $A | grep "XXX" = $B | grep "XXX" then do ..........

I know the position of the word in the first line so I tried using if [ "$A" | awk {'print $5'} = "$B" | awk {'print $2'} ]
but no joy. It didn't like the syntax of that.

Last edited by championc; 04-17-2020 at 01:29 PM..
# 2  
Old 04-17-2020
could you provide a sample/representative snapshot of your input file inputfile and a desired output.
# 3  
Old 04-17-2020
Not clear. Do you want to compare every other line to its predecessor? So, operate on pairs of lines? Or, on every single line? And compare predecessor's field 5 to actual line's field 2? Is it possible that read B hits EOF? How do you handle that?
# 4  
Old 04-17-2020
Thanks for taking the time to reply

I am trying to work with a firewall ruleset. Every DROP rule should have a partner LOG rule. But from the following, you can see that two rules do not have a corresponding LOG rule. So I am trying to process the file and identify all rules I have a DROP but no LOG. The two offenders in this selection below are in BOLD

Code:
set security firewall name Private-to-AA rule 25 action 'drop'
set security firewall name Private-to-AA rule 9999 action 'drop'
set security firewall name Private-to-AA rule 9999 'log'
set security firewall name Private-to-BB default-action 'drop'
set security firewall name Private-to-BB 'default-log'
set security firewall name Private-to-CC default-action 'drop'
set security firewall name Private-to-CC 'default-log'
set security firewall name Private-to-CC rule 9999 action 'drop'
set security firewall name Private-to-CC rule 9999 'log'
set security firewall name Private-to-DD default-action 'drop'
set security firewall name Private-to-DD 'default-log'
set security firewall name Private-to-DD rule 9999 action 'drop'
set security firewall name Private-to-DD rule 9999 'log'
set security firewall name local default-action 'drop'
set security firewall name local rule 10 action 'drop'
set security firewall name local rule 10 'log'

# 5  
Old 04-18-2020
a bit verbose (assuming 'drop' comes first), but....
awk -f cham.awk ruleSetFile.txt where cham.awk is:
Code:
{
  idx=""
  slide=(/drop/)?2:1
  for(i=1;i<=NF-slide;i++)
     idx=(i==1)?$i:idx $i
}
/drop/{d[idx]=$0;next}
/log/ && (idx in d) {delete d[idx]}
END {
  for(i in d)
    print d[i]
}

results in:
Code:
set security firewall name Private-to-AA rule 25 action 'drop'
set security firewall name local default-action 'drop'


Last edited by vgersh99; 04-18-2020 at 08:31 AM..
# 6  
Old 04-18-2020
Great thanks, I'll give that a go. I'm a real BASH noob, so I'd never have managed to get that solution, or anything close to it I think.

Do I need to make a separate script with the contents bring the code in the code section, and then call it from the awk command ? Or can I put the whole lot into a single command that I can paste into a command prompt ?
# 7  
Old 04-18-2020
for simplicity sake.... create a file cham.awk with the content as indicated in the post and execute the command line as indicated in the post.
There're other ways to execute what's been provided, but for now let's stick with the provided paradigm.

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