Decode and pretty print an encoded error message from AWS

decode_aws_error.sh

#!/bin/bash

# grab decoded error message
error=`aws sts decode-authorization-message --encoded-message $@ | jq .DecodedMessage`
# trim the start and end double quotes
json_err=${error:1: -1}
# remove escaped quoted strings and pretty print with jq
echo $json_err | sed 's|\\"|"|g' | jq .

When I run it -, I get error message like the following:

line 9: -1: substituting expression < 0

How are you calling this script?

You should be passing the encoded string into the execution of this script after making it an executable.
e.g. ./decode_aws_error.sh some_encoded_string_here

you need to quote line 6.
json_err="${error:1:-1}"

I worked for me after I changed the code like so.
json_err=${error:1:${#error}-1}

Thanks for you guys works!