jq - concatenate passed arguments with strings

Question

I'm able to use arguments if they are not surrounded by quotes:

var=$(jq -n --arg hostname "my-hostname" '{
  Name: $hostname
}
)

echo $var

Result:

{
  Name: "my-hostname"
}

But I want to concatenate the variable with an existing string, it ignores the value:

var=$(jq -n --arg hostname "my-hostname" '{
  Name: "prefix-value-$hostname"
}
)

echo $var

Result:

{
  Name: "prefix-value-"
}

Expected:

{
  Name: "prefix-value-my-hostname"
}

Answer 1

Replace

"prefix-value-$hostname"

with

"prefix-value-\( $hostname )"

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or

"prefix-value-" + $hostname

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---

Note that since host names can't contain line feeds, -n and --arg could be replaced with -R and stdin.

echo my-hostname | jq -R '{ Name: "prefix-value-\(.)" }'

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