how to write a simple makefile for c

Question

I need to write a simple make file for my.c, and so after

make

then my program can be run by

./my

Answer 1

Well, makefiles are just kind of special scripts. Every is unique, for such simple task this would be sufficient:

Makefile:

CC=gcc
CFLAGS=-lm -lcrypto
SOURCES=my.c cJ/cJ.c

all: my

my: $(SOURCES)
        $(CC) -o my $(SOURCES) $(CFLAGS)

Later you may want to use some other options such as wildcards %.c to compile in multiple files without having to write them in.

Alternatively:

CC=gcc
CFLAGS=-lm -lcrypto

MY_SOURCES = my.c cJ/cJ.c
MY_OBJS = $(patsubst %.c,%.o, $(MY_SOURCES))

all: my

%o: %.c
    $(CC) $(CFLAGS) -c $<

my: $(MY_OBJS)
    $(CC) $(CFLAGS) $^ -o $@

Note that lines following each target ("my:", ...) must start with tab (\t), not spaces.