You can use write attribute tasks to store values in the space created and managed by shell script tasks. Use the shell script tasks to call the values of a write attribute task at a later time.
Use write attribute tasks in workflows to chain task results to other write attribute and shell script tasks. This is important when creating a provisioning workflow. Task results are chained within the same phase of an instance but are not accessible outside of each phase. Using the write attribute task and storing values to the attributes map gives you access to those results to call in other phases of a provisioning workflow.