Bash script: Use string variable in curl JSON Post data

Question

I want to send a json request and embedd a variable in the post data. I did a little research and I came up with the single quotes around the variable.

    #         


        

Answer 1

Update: use the simpler

request_body=$(cat <

rather than what I explain below. However, if it is an option, use jq to generate the JSON instead. This ensures that the value of $FILENAME is properly quoted.

request_body=$(jq -n --arg fname "$FILENAME" '
{
  jsonrpc: "2.0",
  method: "Player.Open",
  params: {item: {file: $fname}}
}'

---

It would be simpler to define a variable with the contents of the request body first:

#!/bin/bash
header="Content-Type: application/json"
FILENAME="/media/file.avi"
request_body=$(< <(cat <

This definition might require an explanation to understand, but note two big benefits:

1. You eliminate a level of quoting
2. You can easily format the text for readability.

First, you have a simple command substitution that reads from a file:

$( < ... )   # bash improvement over $( cat ... )

Instead of a file name, though, you specify a process substitution, in which the output of a command is used as if it were the body of a file.

The command in the process substitution is simply cat, which reads from a here document. It is the here document that contains your request body.