---
title: Makefile
layout: default
---

## Var assignment

    uglify = $(uglify)        # assignment
    compressor := $(uglify)   # lazy assignment
    prefix ?= /usr/local      # safe assignment

## Magic variables

    out.o: src.c src.h
      $@   - "out.o" (target)
      $<   - "src.c" (first prerequisite)
      $^   - "src.c src.h" (all prerequisites)

    %.o: %.c
      $%   - target member name ("foo" in "foo.c")

    also:
      $+   - prerequisites (all, with duplication)
      $?   - prerequisites (new ones)
      $|   - prerequisites (order-only?)
      $*   - basename without extension of the target (?)

      $(@D) - target directory

## Command prefixes

| Prefix | Description |
| ------ | ----------- |
| `-` | Ignore errors |
| `@` | Don't print command |
| `+` | Run even if Make is in 'don't execute' mode |

    build:
        @echo "compiling"
        -gcc $< $@

    -include .depend

## Find files

    js_files  := $(wildcard test/*.js)
    all_files := $(shell find images -name "*")

## Substitutions

    file     = $(SOURCE:.cpp=.o)   # foo.cpp => foo.o
    outputs  = $(files:src/%.coffee=lib/%.js)

    outputs  = $(patsubst %.c, %.o, $(wildcard *.c))
    assets   = $(patsubst images/%, assets/%, $(wildcard images/*))

## More functions

    $(strip $(string_var))

    $(filter %.less, $(files))
    $(filter-out %.less, $(files))

## Building files

    %.o: %.c
      ffmpeg -i $< > $@   # Input and output
      foo $^

## Includes

    -include foo.make

## Options

    make
      -e, --environment-overrides
      -B, --always-make
      -s, --silent

      -j, --jobs=N   # parallel processing

## Conditionals

     foo: $(objects)
     ifeq ($(CC),gcc)
             $(CC) -o foo $(objects) $(libs_for_gcc)
     else
             $(CC) -o foo $(objects) $(normal_libs)
     endif

## Recursive

    deploy:
      $(MAKE) deploy2

## Further reading

 * [isaacs's Makefile](https://gist.github.com/isaacs/62a2d1825d04437c6f08)