Why is involved in building?

• Code is spread into multiple files.
• The final executable has multiple dependencies
• They can have indirect dependencies.
• Need to build when things change
• Build only when things actually change.

Main idea

• User creates a Makefile that mentions dependencies
• The make program reads these dependencies and does required action.

Small example

all : hello

hello: hello.c
    gcc -o hello hello.c

clean:
    rm hello

You can use variables.

CC=gcc

...

hello: hello.c
    ${CC} -o hello hello.c

Stuff that you can do with variables

• Can be set at the command line make FOO=bar target
• Can be given default values.
• Can be used in conditionals.
• Many more stuff.

You can use patterns for compilation

%.html: %.md tweak.css
    ${PANDOC} -s $< -o $@

Phony targets

.PHONY: all clean
all:

clean:

Building subdirectories.

make -C path/to/directory target