3

I have a variable in bash that is an output of Amazon EMR create command;

CLUSTER=$(aws emr create-cluster ...)
echo $CLUSTER

the output is like this:

{ "ClusterId": "j-9YWMBYN98LN7" }

What I need to do is to extract the value j-9YWMBYN98LN7 to a new variable, something like:

ID=$CLUSTER.(ClusterId)

Of course the above command doesn't work. I have tried with jq but no luck.

ID=$(jq -r '.ClusterId' $CLUSTER)

The thing is I'm not even sure what type $CLUSTER is. How do I extract the value j-9YWMBYN98LN7 there? Thanks

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  • if might not matter, but did you try ID=$(jq -r '.ClusterId' "$CLUSTER") ? (dbl-quoting CLUSTER var). Good luck. Commented May 5, 2016 at 2:34
  • Doesn't work either, here is the output: jq: { "ClusterId": "j-1FZMHAPPDD0LG" }: No such file or directory. Thanks anyway Commented May 5, 2016 at 3:24

3 Answers 3

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13

If you want to use jq, you can do it this way

 ID=`echo ${CLUSTER} | jq -r '.ClusterId'`
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5 Comments

Thanks but this doesn't work either. I think this $CLUSTER is not json (may be string, I don't know). Here is the output: cat: {: No such file or directory cat: "ClusterId":: No such file or directory cat: "j-1FZMHAPPDD0LG": No such file or directory cat: }: No such file or directory
My bad, it should be echo instead of cat. I corrected my answer and it should work now.
It works now, thanks a lot, but I can only upvote your answer as I have accepted the other one :)
@user3685928 You can (and should) accept this answer instead.
simple & works 👍✨
5

If

echo $CLUSTER

gives you

{ "ClusterId": "j-9YWMBYN98LN7" }

then

ID=$(awk  'BEGIN{FS="\""}{print $4}' <<< "${CLUSTER}")

should do it.

echo "$ID"
j-9YWMBYN98LN7
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4 Comments

This works. Thanks a lot!
@user3685928 : You're welcome pal !
This solution works in bash, but not in others shells. This is my variation to ash: ID=$(echo $CLUSTER | awk 'BEGIN{FS="\""}{print $4}')
@JavierYáñez Cool, Thankfully the question is tagged bash
2

Try the following:

ID=$(echo "${CLUSTER}" | sed 's/{ "ClusterId": "//' | sed 's/" }//')

That will isolate j-9YWMBYN98LN7, or whatever is between the last set of quotes, into the variable $ID.

I get the feeling there is more to what you need as you are probably planning on using the contents of $ID for something and there may be more efficient ways to capture that value for you. Maybe if you can explain a bit more how you plan on using the value we can provide even more actionable answers.

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3 Comments

I'm writing a script to automate the process of creating an EMR cluster and adding jobs to it. I need this Cluster ID in the job-adding step like this: aws emr add-steps --cluster-id $ID. Again, I'm not sure what type of the variable $CLUSTER here, and I understand that just by giving you guys the output it could be hard
Anyway, the output of your command is still the same as $CLUSTER { "ClusterId": "j-1FZMHAPPDD0LG" }
It is odd that is did not work for you. You can check it via echo '{ "ClusterId": "j-9YWMBYN98LN7" }' | sed 's/{ "ClusterId": "//' | sed 's/" }//' For me it did indeed output j-9YWMBYN98LN7. No worries though, I like @sjsam 's awk answer better as well.

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