Using Makefile to recompile only after changes

We can make use of Makefile features to only recompile our code when the source files changed. This can be achieved because make stats the file system to check whether the target is older than it’s dependencies.

Makefile example

all: main

main: main.o
	gcc main.o -o main

main.o: main.c
	gcc -c main.c

The code above is a toy example. The name before the colon is our target and the name of the file generated by the command bellow it. The name or names after the colon are target’s dependencies.

Running make the first time generates our output, named main in this case. Running make again we get a message stating that our target is up to date make: 'main' is up to date.

Please note that this is just a motivation about one feature of make build system, many improvements can be made on the example to reach a production level Makefile.