jwtd

# JWT decoder
# How to use:
#   token='eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c'
#   1 - echo $token | jwtd
#   2 - jwtd $token
#   # output:
#   # {
#   #  "alg": "HS256",
#   #  "typ": "JWT",
#   #  "sub": "1234567890",
#   #  "name": "John Doe",
#   #  "iat": 1516239022
#   # }

value=${*:-`cat -`}
header=$(jq -R 'split(".") | .[0] | @base64d | fromjson' <<< "$value")
payload=$(jq -R 'split(".") | .[1] | @base64d | fromjson' <<< "$value")

echo "$header $payload" | jq -s add