准备文件

// fun1.c
#include <stdio.h>
void fun1()
{
    printf("this is fun1\n");	

}

// fun2.c
#include <stdio.h>
void fun2()
{
    printf("this is fun2\n");	
}

//head.h
void fun1();
void fun2();
int sum(int len);

//sum.c
#include <stdio.h>

int sum(int len)
{
	int i = 0;
	int sum = 0;
	for(i=0; i<len; i++)
	{
		sum += i;
	}

	return sum;
}

//main.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include "head.h"

int main(int argc, char *argv[])
{
    printf("this is main!\n");
	int i = 0;
	for(i=0; i<argc; i++)
	{
		printf("[%d]:[%s]\n", i, argv[i]);
	}

    fun1();
    fun2();

	printf("sum(10)==[%d]\n", sum(10));

    return 0;
}

Makefile版本一

main: main.c fun1.c fun2.c sum.c
	gcc -o main main.c fun1.c fun2.c sum.c

Makefile版本二

main:main.o fun1.o fun2.o sum.o
	gcc -o main  main.o fun1.o fun2.o sum.o

main.o: main.c
	gcc -c main.c -I./

fun1.o: fun1.c
	gcc -c fun1.c
	
fun2.o: fun2.c
	gcc -c fun2.c

sum.o: sum.c
	gcc -c sum.c

Makefile版本三

target = main
objects = main.o fun1.o fun2.o sum.o
CC = gcc
CPPFLAGS = -I./

#这里的$(objects)不能替换成$^,因为此处是条件，不是命令
$(target): $(objects) 
	$(CC) -o $@ $^

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

###########################################

#main.o: main.c
#	$(CC) -c $< $(CPPFLAGS)

#fun1.o: fun1.c
#	$(CC) -c $<
	
#fun2.o: fun2.c
#	$(CC) -c $<

#sum.o: sum.c
#	$(CC) -c $<

Makefile版本四

target = main

src = $(wildcard *.c)
objects = $(patsubst %.c, %.o, $(src))
#objects = main.o fun1.o fun2.o sum.o

CC = gcc
CPPFLAGS = -I./

#这里的$(objects)不能替换成$^,因为此处是条件，不是命令
$(target): $(objects) 
	$(CC) -o $@ $^

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

###########################################

#main.o: main.c
#	$(CC) -c $< $(CPPFLAGS)

#fun1.o: fun1.c
#	$(CC) -c $<
	
#fun2.o: fun2.c
#	$(CC) -c $<

#sum.o: sum.c
#	$(CC) -c $<

Makefile版本五

target = main
src = $(wildcard *.c)
objects = $(patsubst %.c, %.o, $(src))
CC = gcc
CPPFLAGS = -I./

$(target): $(objects) 
	$(CC) -o $@ $^

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

#clean和前面的命令没有依赖关系
.PHONY: clean
clean:
	rm -f $(objects) $(target)