Unable to assign multiple values from a file to a json request - json

Question

I have a simple file with this test line:
mmm#gmail.com 31460 147557432
My goal is to send as json data.
In my while loop I can echo the variables in the second line of my code example.
However, when I attempt to assign them to jsonstring and echo, the values are not populated.
What do I need to do to pass these values to my json string?
while read emailvar idvar expirevar; do
echo "$emailvar:$expirevar:$idvar"
jsonstring=$idvar $emailvar $expirevar
echo "$jsonstring"
#jsonstring='{"user_id":"$idvar","email":"$emailvar","custom_attributes":{"Program_Expires_at":"$expirevar"}}'
done < "tempdata.txt"

Answer 1

#!/bin/bash
while read line;
do
line_array=($line)
emailvar=${line_array[0]}
expirevar=${line_array[1]}
idvar=${line_array[2]}
jsonstring='{"user_id": "'$idvar'", "email": "'$emailvar'", "custom_attributes":{"Program_Expires_at": "'$expirevar'"}'
echo $jsonstring
done < 'tempdata.txt'
Output:

Answer 2

You have to escape the whitespace to make it part of the string, rather than creating a simple command with some pre-command assignments.
jsonstring=$idvar\ $emailvar\ $expirevar
more commonly written as
jsonstring="$idvar $emailvar $expirevar"
In your commented assignment, you used single quotes, which prevent parameter expansion. You need to use double quotes, which requires manually escaping the interior double quotes. More robust, though, is to use a tool like jq to generate the JSON for you: it will take care of escaping any characters in your variables to generate valid JSON.
jsonstring=$(jq -n \
--arg id "$idvar" \
--arg email "$emailvar" \
--arg expire "$expirevar" \
'{user_id: $id,
email: $email,
custom_attributes: {Program_Expires_at: $expire}}'
)

Answer 3

It seems this is essentially a problem with how bash handles variables and parameter expansion. I believe the solution here basically adding bunch of double quotes.
Double quotes can be used to enable parameter expansion for multiple variables. For JSON output in this bash script, we'll need to use nested double-quotes.
To fix this, we can:
put double quotes (") surrounding the value for jsonstring
escape double quotes surrounding strings used within the value for jsonstring with \
If you'd like $idvar and $expirevar to be interpreted as numbers instead of strings, you don't need escaped double-quotes around these values.
For example:
#!/bin/bash
while read emailvar idvar expirevar; do
jsonstring="{\"user_id\":$idvar,\"email\":\"$emailvar\",\"custom_attributes\":{\"Program_Expires_at\":$expirevar}}"
echo "$jsonstring"
done < "tempdata.txt"
Example output:
user#pc: bash ./script.sh
{"user_id":31460,"email":"mmm#gmail.com","custom_attributes":{"Program_Expires_at":147557432}}
user#pc: bash ./script.sh | jq .
{
"user_id": 31460,
"email": "mmm#gmail.com",
"custom_attributes": {
"Program_Expires_at": 147557432
}
}