#!/bin/bash
json='{"access_token":"kjdshfsd", "key2":"value"}'
echo $json | grep -o '"access_token":"[^"]*' | grep -o '[^"]*$'
IyEvYmluL2Jhc2gKanNvbj0neyJhY2Nlc3NfdG9rZW4iOiJramRzaGZzZCIsICJrZXkyIjoidmFsdWUifScgCiAgICAKZWNobyAkanNvbiB8IGdyZXAgLW8gJyJhY2Nlc3NfdG9rZW4iOiJbXiJdKicgfCBncmVwIC1vICdbXiJdKiQn