Is there any mechanism in Shell script alike “include guard” in C++?

Question

let\'s see an example: in my main.sh, I\'d like to source a.sh and b.sh. a.sh, however, might have already sourced b.sh. Thus it will cause the codes in b.sh executed twice. Is

Answer 1

In bash, an early return does not affect the sourcing file, it returns to it as if the current file were a function. I prefer this method because it avoids wrapping the entire content in if...fi.

if [ -n "$_for_example" ]; then return; fi
_for_example=`date`