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CMake Cookbook recipes.
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_user_name variable in Ch06/Recipe02 #514

Closed ghost closed 5 years ago

ghost commented 5 years ago

Dear Sir,

thanks a lot for your book. Awesome material. In chapter 6, recipe 2 you use built-in variables that I can find nowhere in the official documentation. Searching Google for "cmake '_user_name'" delivers 51 results only. How did you find out about these variables?

Kind regards!

robertodr commented 5 years ago

Hi and thanks for your interest in this project! We use the convention that variables starting with an underscore are defined and used locally within one CMakeLists.txt file. In your specific example all the variables starting with an underscore are used to store the results of invoking CMake commands.

Here we are calling the CMake command execute_process to run (COMMAND argument) the whoami Linux command and saving the result (OUTPUT_VARIABLE argument) into the _user_name local variable.

# Get username
execute_process(
  COMMAND
    whoami
  TIMEOUT
    1
  OUTPUT_VARIABLE
    _user_name
  OUTPUT_STRIP_TRAILING_WHITESPACE
)
ghost commented 5 years ago

Thanks! Missed it, actually!