122 lines
1.9 KiB
Markdown
122 lines
1.9 KiB
Markdown
---
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title: Makefile
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hljs_languages: [makefile]
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layout: 2017/sheet
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---
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## Var assignment
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```makefile
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uglify = $(uglify) # assignment
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compressor := $(uglify) # lazy assignment
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prefix ?= /usr/local # safe assignment
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```
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## Magic variables
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```makefile
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out.o: src.c src.h
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$@ # "out.o" (target)
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$< # "src.c" (first prerequisite)
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$^ # "src.c src.h" (all prerequisites)
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%.o: %.c
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$* # the 'stem' with which an implicit rule matches ("foo" in "foo.c")
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also:
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$+ # prerequisites (all, with duplication)
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$? # prerequisites (new ones)
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$| # prerequisites (order-only?)
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$(@D) # target directory
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```
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## Command prefixes
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| Prefix | Description |
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| ------ | ----------- |
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| `-` | Ignore errors |
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| `@` | Don't print command |
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| `+` | Run even if Make is in 'don't execute' mode |
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```makefile
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build:
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@echo "compiling"
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-gcc $< $@
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-include .depend
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```
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## Find files
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```makefile
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js_files := $(wildcard test/*.js)
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all_files := $(shell find images -name "*")
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```
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## Substitutions
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```makefile
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file = $(SOURCE:.cpp=.o) # foo.cpp => foo.o
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outputs = $(files:src/%.coffee=lib/%.js)
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outputs = $(patsubst %.c, %.o, $(wildcard *.c))
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assets = $(patsubst images/%, assets/%, $(wildcard images/*))
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```
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## More functions
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```makefile
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$(strip $(string_var))
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$(filter %.less, $(files))
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$(filter-out %.less, $(files))
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```
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## Building files
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```makefile
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%.o: %.c
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ffmpeg -i $< > $@ # Input and output
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foo $^
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```
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## Includes
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```makefile
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-include foo.make
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```
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## Options
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```sh
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make
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-e, --environment-overrides
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-B, --always-make
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-s, --silent
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-j, --jobs=N # parallel processing
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```
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## Conditionals
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```makefile
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foo: $(objects)
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ifeq ($(CC),gcc)
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$(CC) -o foo $(objects) $(libs_for_gcc)
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else
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$(CC) -o foo $(objects) $(normal_libs)
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endif
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```
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## Recursive
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```makefile
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deploy:
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$(MAKE) deploy2
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```
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## Further reading
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* [isaacs's Makefile](https://gist.github.com/isaacs/62a2d1825d04437c6f08)
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