Passing bash variable to jq
JsonBashEnvironment VariablesJqJson Problem Overview
I have written a script to retrieve certain value from file.json. It works if I provide the value to jq select, but the variable doesn't seem to work (or I don't know how to use it).
#!/bin/sh
#this works ***
projectID=$(cat file.json | jq -r '.resource[] | select(.username=="[email protected]") | .id')
echo "$projectID"
[email protected]
#this does not work *** no value is printed
projectID=$(cat file.json | jq -r '.resource[] | select(.username=="$EMAILID") | .id')
echo "$projectID"
Json Solutions
Solution 1 - Json
Consider also passing in the shell variable (EMAILID) as a jq variable (here also EMAILID, for the sake of illustration):
projectID=$(jq -r --arg EMAILID "$EMAILID" '
.resource[]
| select(.username==$EMAILID)
| .id' file.json)
Postscript
For the record, another possibility would be to use jq's env function for accessing environment variables. For example, consider this sequence of bash commands:
EMAILID[email protected] # not exported
EMAILID="$EMAILID" jq -n 'env.EMAILID'
The output is a JSON string:
"[email protected]"
Solution 2 - Json
I resolved this issue by escaping the inner double quotes
projectID=$(cat file.json | jq -r ".resource[] | select(.username==\"$EMAILID\") | .id")
Solution 3 - Json
Posting it here as it might help others. In string it might be necessary to pass the quotes to jq. To do the following with jq:
.items[] | select(.name=="string")
in bash you could do
EMAILID=$1
projectID=$(cat file.json | jq -r '.resource[] | select(.username=='\"$EMAILID\"') | .id')
essentially escaping the quotes and passing it on to jq
Solution 4 - Json
Little unrelated but I will still put it here, For other practical purposes shell variables can be used as -
value=10
jq '."key" = "'"$value"'"' file.json
Solution 5 - Json
It's a quote issue, you need :
projectID=$(
cat file.json | jq -r ".resource[] | select(.username=='$EMAILID') | .id"
)
If you put single quotes to delimit the main string, the shell takes $EMAILID literally.
"Double quote" every literal that contains spaces/metacharacters and every expansion: "$var", "$(command "$var")", "${array[@]}", "a & b". Use 'single quotes' for code or literal $'s: 'Costs $5 US', ssh host 'echo "$HOSTNAME"'. See
<http://mywiki.wooledge.org/Quotes>
<http://mywiki.wooledge.org/Arguments>
<http://wiki.bash-hackers.org/syntax/words>
Solution 6 - Json
Jq now have better way to access environment variables, you can use env.EMAILID:
projectID=$(cat file.json | jq -r ".resource[] | select(.username==env.EMAILID) | .id")
Solution 7 - Json
Another way to accomplish this is with the jq "--arg" flag. Using the original example:
#!/bin/sh
#this works ***
projectID=$(cat file.json | jq -r '.resource[] |
select(.username=="[email protected]") | .id')
echo "$projectID"
[email protected]
# Use --arg to pass the variable to jq. This should work:
projectID=$(cat file.json | jq --arg EMAILID $EMAILID -r '.resource[]
| select(.username=="$EMAILID") | .id')
echo "$projectID"
See here, which is where I found this solution: https://github.com/stedolan/jq/issues/626
Solution 8 - Json
I know is a bit later to reply, sorry. But that works for me.
export K8S_public_load_balancer_url="$(kubectl get services -n ${TENANT}-production -o wide | grep "ingress-nginx-internal$" | awk '{print $4}')"
And now I am able to fetch and pass the content of the variable to jq
export TF_VAR_public_load_balancer_url="$(aws elbv2 describe-load-balancers --region eu-west-1 | jq -r '.LoadBalancers[] | select (.DNSName == "'$K8S_public_load_balancer_url'") | .LoadBalancerArn')"
In my case I needed to use double quote and quote to access the variable value.
Cheers.
Solution 9 - Json
In case where we want to append some string to the variable value and we are using the escaped double quotes, for example appending .crt to a variable CERT_TYPE; the following should work:
$ CERT_TYPE=client.reader
$ cat certs.json | jq -r ".\"${CERT_TYPE}\".crt" #### This will *not* work #####
$ cat certs.json | jq -r ".\"${CERT_TYPE}.crt\""
Solution 10 - Json
I also faced same issue of variable substitution with jq. I found that --arg is the option which must be used with square bracket [] otherwise it won't work.. I am giving you sample example below:
RUNNER_TOKEN=$(aws secretsmanager get-secret-value --secret-id $SECRET_ID | jq '.SecretString|fromjson' | jq --arg kt $SECRET_KEY -r '.[$kt]' | tr -d '"')