how to output awk result to varial - shell

Question

i need to run hadoop command to list all live nodes, then based on the output i reformat it using awk command, and eventually output the result to a variable, awk use different delimiter each time i call it:
hadoop job -list-active-trackers | sort | awk -F. '{print $1}' | awk -F_ '{print $2}'
it outputs result like this:
hadoop-dn-11
hadoop-dn-12
...
then i put the whole command in variable to print out the result line by line:
var=$(sudo -H -u hadoop bash -c "hadoop job -list-active-trackers | sort | awk -F "." '{print $1}' | awk -F "_" '{print $2}'")
printf %s "$var" | while IFS= read -r line
do
echo "$line"
done
the awk -F didnt' work, it output result as:
tracker_hadoop-dn-1.xx.xsy.interanl:localhost/127.0.0.1:9990
tracker_hadoop-dn-1.xx.xsy.interanl:localhost/127.0.0.1:9390
why the awk with -F won't work correctly? and how i can fix it?

Answer 1

var=$(sudo -H -u hadoop bash -c "hadoop job -list-active-trackers | sort | awk -F "." '{print $1}' | awk -F "_" '{print $2}'")
Because you're enclosing the whole command in double quotes, your shell is expanding the variables $1 and $2 before launching sudo. This is what the sudo command looks like (I'm assuming $1 and $2 are empty)
sudo -H -u hadoop bash -c "hadoop job -list-active-trackers | sort | awk -F . '{print }' | awk -F _ '{print }'"
So, you see your awk commands are printing the whole line instead of just the first and 2nd fields respectively.
This is merely a quoting challenge
var=$(sudo -H -u hadoop bash -c 'hadoop job -list-active-trackers | sort | awk -F "." '\''{print $1}'\'' | awk -F "_" '\''{print $2}'\')
A bash single quoted string cannot contain single quotes, so that's why you see ...'\''... -- to close the string, concatenate a literal single quote, then re-open the string.
Another way is to escape the vars and inner double quotes:
var=$(sudo -H -u hadoop bash -c "hadoop job -list-active-trackers | sort | awk -F \".\" '{print \$1}' | awk -F \"_\" '{print \$2}'")