How to extract string field value from a URL using regular expression in shell script?

Question

I am working on a project in which I need to make a url call to one of my server from the bash shell script..

http://hostname.domain.com:8080/beat

After hitting the above url, I will be getting the below response which I need to parse it and extract value of state from it

num_retries_allowed: 3 count: 30 count_behind: 100 state: POST_INIT num_rounds: 60 hour_col: 2 day_col: 0

Now I want to extract state variable value using regular expressions. I am able to extract count and count_behind value from it but not sure how to extract state value from it.

#send the request, put response in variable
DATA=$(wget -O - -q -t 1 http://hostname.domain.com:8080/beat)

#grep $DATA for count and count_behind
COUNT=$(echo $DATA | grep -oE 'count: [0-9]+' | awk '{print $2}')
COUNT_BEHIND=$(echo $DATA | grep -oE 'count_behind: [0-9]+' | awk '{print $2}')

# how to extract state variable value here?
STATE= what do I add here?

Also if in $DATA if state variable is not there by any chance, then I want to assign 0 to STATE variable. After that I want to verify the conditionals and exit out of the script depending on that.

If STATE is equal to POST_INIT then exit successfully out of the shell script or STATE is equal to 0, then exit successfully as well.

#verify conditionals
if [[ $STATE -eq "POST_INIT" || $STATE -eq "0" ]]; then exit 0; fi

anubhava · Accepted Answer · 2015-02-03 19:06:59Z

1

You can use this grep -P:

state=$(grep -oP 'state: \K\S+' <<< "$DATA")   
[[ -z "$state" ]] && state=0
echo "$state"
POST_INIT

edited Feb 3, 2015 at 19:06

answered Feb 3, 2015 at 18:00

anubhava

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6 Comments

john Over a year ago

Thanks anubhava. How do I assign zero value if state is missing by any chance in the $DATA?

anubhava Over a year ago

After grep command you can just do: [[ -z "$state" ]] && state=0

john Over a year ago

Yes that's what I meant, meaning if state: string is missing in input. Can you update your answer with this as well so that it is complete?

john Over a year ago

Cool. Thanks. Can you explain little bit how this works if state: string is missing then how will it assign 0 to it and how will it work in normal case. Just for my understanding purpose.

anubhava Over a year ago

If state: is missing in input then grep's output is empty and hence state variable is also empty. And -z "$state" is check for emptiness of variable. Part after && executed if left hand condition evaluates to true.

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