Use output of 'jq' on a curl command as a condition in a while loop

Question

I want this statement to keep looping while the value of the json field in this api response is null.

while $(curl --location --request GET "https://example.com/integration-test/results/json"| jq '.result') == null
    do
    echo "Waiting for Integration tests to finish. Trying again in 10 seconds."
    sleep 2
done

The == null obviously doesn't work, but its illustrative of what I'm going for. When the Integration tests finish this api call will instead return SUCCESS or FAILURE in 'result'. Thats when I want the loop to stop.

What is the output of the wget ... | jq ... command that you want to test for? Is it actually going to be the string "null", or just nothing, or something else? — Gordon Davisson
– Gordon Davisson, Commented Jan 14, 2021 at 21:37

Charles Duffy · Accepted Answer · 2021-01-14 21:53:25Z

3

Consider using the -e argument to jq to make its exit status reflect its output (emitting a failed exit status when the only output is either null or false).

Writing the code below for clarity rather than terseness (using explicit grouping operators to make it clear that the negation applies to the entire pipeline):

#!/usr/bin/env bash
set -o pipefail  # make a failure on the left-hand side fail the entire pipeline
while ! { curl --fail -L "https://example.com/integration-test/results/json" \
          | jq -e '.result' >/dev/null; }; do
    echo "Waiting for Integration tests to finish. Trying again in 10 seconds."
    sleep 10
done

answered Jan 14, 2021 at 21:53

Charles Duffy

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Comments

Barmar · Accepted Answer · 2021-01-14 21:27:32Z

0

You need to put the comparison in a conditional expression.

while [[ "$(curl --location --request GET "https://example.com/integration-test/results/json"| jq '.result')" == null ]]
do
    ...
done

answered Jan 14, 2021 at 21:27

Barmar

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1 Comment

Barmar Over a year ago

Unfortunately my jq knowledge is very rudimentary. That would be a good alternate answer.

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