My Notes on Makefiles

Stuff I use most

Output Functions

$(info ...) - Print out some info message
$(warning ...) - Print out a warning
$(error ...) - Print out an error and STOP

Defines

D = something - Set D equal to 'something' every time D is used (expand every time)
D := something - Set D equal to 'something' once (expand only once. non-recursive)
D ?= something - Set D equal to 'something' only if not already set

Functions

$(shell <command>) - Run 'command' in a shell and return output
$(call var,arg,arg,...) - Call a function, var, with args.

call example:
reverse = $(2) $(1)
D = $(call reverse,a,b) # D will contain 'b a'

$(filter pat,text) - Filter 'text' by 'pat'

filter example:
D = a.h a.c b.h b.c
CFiles = $(filter %.c,$(D))  # CFiles will contain 'a.c b.c' only

$(if <cond>,<then>,<else>) - If 'cond' is non-empty string, do 'then'...
$(or arg,arg,...) - Return first non-empty arg or empty string
$(and arg,arg,...) - Return empty string or last non-empty arg

List Functions

$(sort <list>) - Sort list
$(firstword list) - Return first item in space-separated list
$(lastword list) - Return last item in space-separated list
$(word nth,list) - Return 1-based nth word in list
$(words list) - Return the number of words in space-separated list
$(wordlist start,end,list) - Return words from start to end in list

Directory/Path/File Functions

$(abspath ...) - Get absolute path of a file and don't check for existence
$(realpath ...) - Get real path of a file and return empty string if it doesn't exist
$(wildcard <pattern>) - Get list of files matching 'pattern'

Create/Append to File

$(file >$(log),stuff) - Write 'stuff' to log file