Makefile templates topic on GitHub - makefile-template

Targets (commands) will differ per project and environment but these can be applied where relevant.

Remember, the make command also supports tab autocomplete for targets.

For language specific examples, see my Code Cookbook project’s make section.

Phony

Phony is useful if your target matches an actual directory but you don’t want to make to run against it. Normally, you could run make DIR for compiling a C program or similar, but that isn’t helpful outside of compiled languages.

This can be done at the start, or just before each target.

Here we use PHONY where foo and docs are actual directories as well targets.

  • Makefile 
      .PHONY: foo docs

  foo:
      echo 'Foo'

  docs:
      echo 'Test'
  • Makefile 
      .PHONY: foo
  foo:
      echo 'Foo'
		
  .PHONY: docs
  docs:
      echo 'Test'

Some people like to add .PHONY to every target, whether in just above each or all at the top of the file. In many cases, this adds no benefit, maybe more useful for C and C++ projects with compile steps where you might have fixed or dynamically generated folders which match commands. However, the often it serves no purpose and just clutters the file. Rather use .PHONY where it is needed (like if you do have a folder where yours docs will get generated).

Comments

You can put a comment anywhere.

The comment will be printed when the target runs. But you can use @# to prevent it from printing.

  • Makefile 
      # Comment.
  foo: # Another comment.
      # Yet another comment.
      @# This comment won't be printed.
      echo 'Foo'

Export

Use variables in commands.

Given file .env with variable set as FOO=bar and script_that_echoes_foo.sh which does echo $FOO.

Do this

The combination of export and source works well.

  • Makefile 
      export FOO=''

  test:
    source .env && echo $$FOO
    source .env && ./script_that_echoes_foo.sh

Don’t do this

The following will not work as expected ,due to make limitations on environment setting of child processes.

  • Makefile 
      test:
      source .env
      echo $$FOO

The following will not work either, with or without export set at the top.

  • Makefile 
      test:
      export $(<.env) && ./script_that_echoes_foo.sh

Control flow

Using conditionals and iteration, similar to shell.

Note that unlike in the shell, the \ is necessary in a Makefile so that the command is combined on one line at run at once.

For

  • Makefile 
      foo:
      for bar in my-dir/*; do \
          export fizz=$$(echo $$bar) \
          $(MAKE) plan; \
      done

If

Note lack of indentation.

  • Makefile 
      TARGET:
  ifneq (CONDIITION, )
      ACTION
  endif
      ACTION

Syntax in Make docs.

Example:

  • Makefile 
      libs_for_gcc = -lgnu
  normal_libs =

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

Alternate:

  • Makefile 
      TARGET:
      @if [ CONDITION ]; then \
          ACTION ; \
      fi

Get the current target name

  • Makefile 
      a:
      echo $(@)
  b:
      echo $(@)

Shell usage:

$ make a b
echo a
a
echo b
b

Find files

Wildcard

Using wildcard to evaluate a globstar.

This will only search at the directory level given - not subdirectories.

Don’t quote the glob.

files  := $(wildcard *.lock)

a:
	@echo $(all_files)

$ make a
Gemfile.lock

Or in a directory.

# Top-level.
docs := $(wildcard *.md)
# CONTRIBUTING.md README.md about.md index.md

# Target directory.
docs := $(wildcard docs/*.md)
# docs/README.md docs/deploy.md docs/development.md docs/installation.md docs/usage.md

# Exactly one level down in any directory. Ignores top-level and 2 levels down.
docs := $(wildcard */*.md)
# _site/about.md docs/README.md docs/deploy.md docs/development.md docs/installation.md docs/usage.md resources/index.md

Note using **/*.md will not work for finding the current directory like if using with grep. For Make wildcards, it will still search one level below the current directory.

Shell find

Evaluate a shell expression and using find command inside it. Quote the glob.

This does not work if you leave out :=, $() or shell.

This will search in subdirectories.

files := $(shell find . -name "*.lock")

a:
	@echo $(all_files)

$ make a
./Gemfile.lock ./vendor/bundle/ruby/2.7.0/gems/http_parser.rb-0.6.0/Gemfile.lock

Note that is an array moved to one line.

Here is the original output:

$ find . -name '*.lock'
./Gemfile.lock
./vendor/bundle/ruby/2.7.0/gems/http_parser.rb-0.6.0/Gemfile.lock