Send data with curl in Bash script: positional argument not working - json

Question

Total noob in BASH. Trying to learn.
I have the following bash script to make an API request:
#!/bin/bash
if [ $1 = "new_event" ]; then
a='https://www.googleapis.com/calendar/v3/calendars/'
b=$2
c='/events?access_token='
d=$3
path=$a$b$c$d
echo $4
OUTPUT="$(curl -s -H "Content-Type: application/json" $path -d $4 )"
echo "${OUTPUT}"
fi
Positional arguments are 'new_event', calendarId, access token and json string.
If I run the script I get:
first echo is the json string I pass as parameter in the call:
' {"guestsCanSeeOtherGuests": false, "location": "", "description": "TEST", "reminders": {"useDefault": false}, "start": {"dateTime": "2017-07-06T14:00:00", "timeZone": "America/Sao_Paulo"}, "end": {"dateTime": "2017-07-06T15:00:00", "timeZone": "America/Sao_Paulo"}, "guestsCanInviteOthers": false, "summary": "TEST", "status": "tentative", "attendees": []} '
second echo gives me parsing error.
BUT, if I copy the echoed json string and replace $4 for it, everything works.
OUTPUT="$(curl -s -H "Content-Type: application/json" $path -d ' {"guestsCanSeeOtherGuests": false, "location": "", "description": "TEST", "reminders": {"useDefault": false}, "start": {"dateTime": "2017-07-06T14:00:00", "timeZone": "America/Sao_Paulo"}, "end": {"dateTime": "2017-07-06T15:00:00", "timeZone": "America/Sao_Paulo"}, "guestsCanInviteOthers": false, "summary": "TEST", "status": "tentative", "attendees": []} ' )"
Any hint why is it not working with the positional argument while it works if I paste it's content?
Thanks!

Answer 1

When you pass the JSON string as a parameter, it assigns the content contained inside the single quote as a whole string but when you pass it to curl it was subjected to word splitting.
To show what it looks like here's a sample script to demonstrate it.
This script will receive the string and pass it to the second script.
#!/bin/bash
./params $1
This second script simulates what curl sees. It will print the number of parameters it receives.
#!/bin/bash
echo $#
Guess what the output is:
27
To fix your issue and make it simpler, drop the outermost quote and quote everything inside the $().
OUTPUT=$(curl -s -H "Content-Type: application/json" "$path" -d "$4" )