in a shell script:

function_name # call the function
return_val=$? # store the return value
echo $return_val # do something with the return value

Function can return a value, called an exit status

The exit status may be explicitly specified by a return statement, otherwise it is the exit status of the last command in the function

This exit status may be used in the script by referencing it as $?

The largest positive integer a function can return is 255