Why are Makefiles in Linux so useful?

Question

I want to know why makefiles in Linux are so useful (I mean in the practical sense). Why can't we just compile all our programs in the normal way?

Answer 1

Makefiles do so much work for you, and are frequently more powerful than people realize. Take the following simple makefile

 all: helloworld

that's one line, and (gnu make, at least) would know to run cc -o helloworld helloworld.c Then, as the project grows, you add one more rule:

helloworld: helloworld.o ui.o xml.o mailcomponent.o
   $(CC) -o $@ $@.c $^ $(LDLAGS)

and make knows to run

cc -c ui.c
cc -c xml.c
cc -c mailcomponent.c
cc -c helloworld.c
cc -o helloworld helloworld.o ui.o xml.o mailcomponent.o

Then say you want to optimize everything.

CFLAGS=-O2

at the beginning of the file takes care of you.

When the project gets larger, make keeps track of the files which have and haven't changed, preventing extraneous, and time-consuming re-compiles.

Makefiles are wonderful timesavers, and I haven't even touched on more advanced recipes.