How to use shell variables in MQTT

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Hi,
I am new to shell scripting and MQTT.
I need to publish a `JSON file` using `MQTT`. We can do it by storing the JSON contents in a `shell variable` and then using it in MQTT publish command. But it is not working for me.

Please help me out to get the output. Whether I need to add some more code in the shell script. I don't know how to proceed.

What I have tried:

my shell script:
```var1="{"name":"Harini", "age":24, "city":"NewYork", "message":"Hello world"}"```

my Mosquitto commands:
```mosquitto_pub -h localhost -t "test" -m {\"Contents\":$var1}```
```mosquitto_sub -h localhost -t "test"```

Output I got:
```{"Contents":}```
Expected Output:
```{"Contents":{"name":"Harini", "age":24, "city":"NewYork", "message":"Hello world"}}```

Posted 6-May-21 0:20am

Stefen20000

Updated 8-Jun-21 7:07am

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QuantumPlumber · Answer 1 · 2021-06-08T07:07:00

I think the outer enclosing set of double quotes in your var1=.... statement might need to be single quotes (I assume the triple-quotes are just there for show and not what you actually typed). I have no familiarity with mosquitto but have had a few wrestling matches with shell syntax over the year . . . using "echo" as a mosquitto substitute fixed it for me . . .

var2='{"name":"Harini", "age":24, "city":"NewYork", "message":"Hello world"}'
echo {\"Contents\":$var2}
{"Contents":{"name":"Harini", "age":24, "city":"NewYork", "message":"Hello world"}}

var3="{"name":"Harini", "age":24, "city":"NewYork", "message":"Hello world"}"
bash: world}: command not found...
echo $var3

Might possibly be shell-dependent (I was using bash).