And than execute make target, it executes command. Last time ago i started to learn some low-level stuffs as assembly programming, operating system theory and practice (as you can read and understand from previous blog posts about assembly programming). Some days ago i started to read Linux kernel Makefile and here i want to share some make syntax features which i learned from there. So this post is not for people who used make much time and knows much about it.
origin - is a builtin function which returns information about variable. It's general form is:
You can pass any $(variable) to it and it will return info about it. Return value of origin can be:
- undefined - variable didn't defined
- default - default var, like $(CC) and etc...
- environemnt - from environment
- environment override - return environemnt which was overridden with make -e
- file - from makefile
- command line - from make command line arguments
- automatic - see bellow
Usually makefile prints every action after executing it, but sometimes we no need in it. We can use @ prefix for it, for example:
In this way make will not print @echo "Done." line, but just prints Done.
filter function removes all space separated words from text, which doesn't match no one template. General view of it:
For example, we have targets list and we need to check is there build target there or not:
Check empty value
We can check empty value with following:
Previously when i was need to get current directory path, i used something like this:
Now i know about builtin variable:
Errors, Warning and Info
There are 3 builtin functions for printing errors, warning and info:
VPATH variable defines list of directories where template rules will search dependencies:
There are some special macros:
- $| - Names of all the order-only prerequisites, with spaces between them
- $@ - Filename of the target of the rule
- $? - Names of all the prerequisites that are newer than the target
- $< - Name of the first prerequisite
This is all. If you will have any question or suggestions, please write me a comment or ping me in twitter.
English is not my first language, so you'll find mistakes in blog post please write me in comments or drop me email .