How to view the value of a variable in makfile

Checking the value of a variable in makefile should be a very troublesome problem, but this is a very convenient method developed by the great god himself. This method is very simple. The introduction is as follows:

If a variable src_file is used in a very complicated and huge MAKEFILE file, you 'd like to know the value of this variable when makefile runs here. Then you can write two lines below this variable:

$ (Shell echo $ (src_file)> readme.txt)

Rrrrrrrrrrrrrrrrrrr

The first line is actually to call the shell command to input the value of this variable into the README variable. The shell command in makefile is executed first than the rule command, so it can certainly be run here. The "rrrrrrrrrrrrrrrrrrrrrrrrrrr" in the second line is actually a production error. Because some makefiles have been executed for a long time, we just want to know the value of the variable src_file, you do not need to execute the complete makefile again. Therefore, if you add a incorrectly formatted code to the second line, the makefile will exit after executing the shell command.

This is complete!