# Writing Makefiles

## Pattern rules

In prerequesite, use exactly one `%`. Can then be used in requirements. E.g.

    %.o: %.c
        # compile .c file to .o

Details: <https://www.gnu.org/software/make/manual/html_node/Pattern-Rules.html>

## Automatic variables

* `$@`: current target
* `$<`: first prerequisite
* `$^`: all prerequisites, separated by spaces
* `$*`: target without extension
* `$(@F)`: file-within-directory part of target path

More: <https://www.gnu.org/software/make/manual/html_node/Automatic-Variables.html>

## C-related flags

* `CC`: C compiler
* `CFLAGS`: flags for `CC`
* `LDFLAGS`: flags for the linker

## Text functions

* `$(var:suffix=replacement)`, syntax sugar for
  `$(patsubst %suffix, $replacement, $(var))`

More: <https://www.gnu.org/software/make/manual/html_node/Text-Functions.html>

## Filename functions

<https://www.gnu.org/software/make/manual/html_node/File-Name-Functions.html>

## Recipes

* `@<command>`: don't print command ran
* `-<command>`: don't exit on command failure

## Arguments

* `-B, --always-make`: force to make all targets