Simple and Fast IPC mechanism between two shell scripts

I have two shell applications and one starts to run after the other exits. I need to set a flag from the first shell application. From the second shell application, I need to check whether the flag is true or false. What is the simplest way to do it? As they don't run simultaneously I can't use named pipes. Writing to a file seems complicated. What are some other mechanisms to achieve this?

Simple and Fast IPC mechanism between two shell scripts
 
 
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