Cannot use/pass shell variables using jq on command line - environment-variables

Question

I am fairly new to jq and I am using this tutorial to add a new Org to a hyperledger fabric network.
There is extensive use of jq throughout the tutorial, especially modifying json files.
The tutorial uses an example Org name but I am trying to make the org name dynamic. Everything works out well except when I try to pass variables to jq.
Here are the jq commands and their outputs.
jq version: 1.5.1
$ export MSPID=Org4MSP
$ echo $MSPID
Org4MSP
Trying to pass the variable using env.
Keyword: env.MSPID
$ jq -s '.[0] * {"channel_group":{"groups":{"Application":{"groups": {"env.MSPID":.[1]}}}}}' config.json org4.json
Output snippet: Instead of printing Org4MSP, it prints the literal string env.MSPID
"env.MSPID": {
"groups": {},
"mod_policy": "Admins",
"policies": {
"Admins": {
"mod_policy": "Admins",
"policy": {
"type": 1,
"value": {
"identities": [
{
Trying to pass the variable using --arg option
Keyword: "$MSP"
jq --arg MSP "$MSPID" -s '.[0] * {"channel_group":{"groups":{"Application":{"groups": {"$MSP":.[1]}}}}}' config.json org4.json
Output snippet: Instead of printing Org4MSP, it prints the literal string $MSP
"$MSP": {
"groups": {},
"mod_policy": "Admins",
"policies": {
"Admins": {
"mod_policy": "Admins",
"policy": {
"type": 1,
"value": {
"identities": [
{
Trying to pass a variable using --arg option and without using double quotes:
keyword: $MSP
$ jq --arg MSP "$MSPID" -s '.[0] * {"channel_group":{"groups":{"Application":{"groups": {$MSP:.[1]}}}}}' config.json org4.json
jq: error: syntax error, unexpected ':', expecting '}' (Unix shell quoting issues?) at , line 1:
.[0] * {"channel_group":{"groups":{"Application":{"groups": {$MSP:.[1]}}}}}
jq: 1 compile error
Trying to pass variable using env. and without double quotes:
keyword: env.MSPID
$ jq -s '.[0] * {"channel_group":{"groups":{"Application":{"groups": {env.MSPID:.[1]}}}}}' config.json org4.json
jq: error: syntax error, unexpected FIELD, expecting '}' (Unix shell quoting issues?) at , line 1:
.[0] * {"channel_group":{"groups":{"Application":{"groups": {env.MSPID:.[1]}}}}}
jq: 1 compile error
I apologize if this seems to be a trivial question but I have searched online and in docs and do not understand why the JSON key will not convert to the shell variable's value.
Thank you

Answer 1

Environment variables
In your sub-expression:
{"env.MSPID":.[1]}
you have quoted env.MSPID thereby making it a literal string. Since you want to invoke the env function, you should instead write:
{ (env.MSPID):.[1]}
The parentheses are needed to ensure that jq will evaluate the parenthesized expression properly.
{$MSP:.[1]}
As noted above, when an expression must be evaluated to determine the string-value of a key, the expression must be parenthesized, e.g.
{($MSP):.[1]}