#!/bin/bash
s='"assets" : [ {
  "downloadUrl" : "https://URL/repository/doc/v&/PROJECT/SUBP/csc-dbc1-repo01x-x11-20210301/DIR/DIR2",
  "path" : "v&/PROJECT/SUBP/csc-dbc1-repo01x-x11-20210301/DIR/DIR2",'
grep -Eo -i 'csc-[a-z0-9]{4}-[a-z0-9]+-[a-z0-9]{3}-[0-9]{8}' <<< "$s"