Makefile Reference

v1.0.0

Rules, variables, functions, directives, and automatic variables for GNU Make.

18 entries found

RuleRule

target: prerequisites
	recipe

The fundamental unit of a Makefile. target is built by running recipe when any prerequisite is newer or target doesn't exist. The recipe must be indented with a real TAB character.

build:
	go build -o bin/app ./cmd/app

.PHONYRule

.PHONY: target1 target2

Declares targets that are not actual files. Without this, Make would skip the recipe if a file with the target name exists.

.PHONY: build test clean

build:
	npm run build

clean:
	rm -rf dist/

.DEFAULT_GOALRule

.DEFAULT_GOAL := target

Sets the target used when make is invoked with no arguments. Without this, the first non-special target is the default.

.DEFAULT_GOAL := help

help:
	@echo "Usage: make [target]"

Variable assignmentVariable

NAME = value | NAME := value | NAME ?= value | NAME += value

= deferred expansion, := immediate expansion, ?= assign if unset, += append. Use := for performance in large Makefiles.

CC      := gcc
CFLAGS  := -Wall -O2
SRCS    ?= $(wildcard src/*.c)

overrideDirective

override NAME = value

Overrides a variable set on the command line. Normally, command-line values take precedence over Makefile assignments.

override CFLAGS += -g

$@Auto-var

$@

The target name of the current rule.

%.o: %.c
	$(CC) -c -o $@ $<

$<Auto-var

$<

The first prerequisite.

%.o: %.c
	$(CC) $(CFLAGS) -c $< -o $@

$^Auto-var

$^

All prerequisites (deduplicated).

app: main.o utils.o
	$(CC) -o $@ $^

$*Auto-var

$*

The stem of a pattern rule (the part matched by %).

%.tar.gz: %
	tar czf $@ $*

$?Auto-var

$?

All prerequisites that are newer than the target.

archive.a: $(OBJS)
	ar r $@ $?

$(wildcard ...)Function

$(wildcard pattern)

Returns a space-separated list of existing files matching the glob pattern.

SRCS := $(wildcard src/*.c)
HDRS := $(wildcard include/*.h)

$(patsubst ...)Function

$(patsubst pattern,replacement,text)

Performs pattern substitution. % in pattern matches any sequence of characters, and the same sequence replaces % in the replacement.

OBJS := $(patsubst src/%.c,build/%.o,$(SRCS))

$(filter ...)Function

$(filter pattern,text)

Returns only the words in text that match the pattern. $(filter-out) returns words that do NOT match.

C_FILES := $(filter %.c, $(ALL_FILES))

$(foreach ...)Function

$(foreach var,list,text)

Iterates over a list, expanding text with var bound to each word.

DIRS := a b c
paths := $(foreach d,$(DIRS),src/$(d))

$(shell ...)Function

$(shell command)

Runs a shell command and returns its stdout (newlines replaced with spaces).

VERSION := $(shell git describe --tags --abbrev=0)
DATE    := $(shell date +%Y-%m-%d)

$(subst ...)Function

$(subst from,to,text)

Replaces every occurrence of from with to in text. Unlike patsubst, does not support % patterns.

CSV := a,b,c
LIST := $(subst ,, ,$(CSV))

includeDirective

include <filename> | -include <filename>

Includes another Makefile. Prefix with - to silently ignore missing files. Useful for generated dependency files.

-include build/.deps/*.d

ifeq / ifneq / ifdef / ifndefDirective

ifeq (a,b) ... else ... endif

Conditional evaluation. ifeq tests equality; ifdef tests if a variable is non-empty.

ifeq ($(OS),Windows_NT)
  EXE := .exe
else
  EXE :=
endif