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Linux系统下，一些公用的函数我们常常生成一个函数库，方便其它函数调用、链接。静态库编译时会直接链接到主函数中，运行时就不需要了。动态库反之，在运行主函数时才会链接。
1. Use the Vim editor to prepare the sample program in advance
1、main.c
#include <stdio.h>
#include "sub.h"
int mian()
{
int num1 = 3, num2 = 4;
print_hello();
printf("num1 x num2 = %.2f\n",sub(num1,num2));
printf("num1 + num2 = %.2f\n",sub1(num1,num2));
return 0;
}
2、sub.c / sub.h
#include "sub.h"
float sub(int num1, int num2)
{
return (num1 * num2);
}
float sub1(int num1, int num2)
{
return (num1 + num2);
}
#ifndef __SUB_H__
#define __SUB_H__
#include <stdio.h>
float sub(int num1, int num2);
float sub1(int num1,int num2);
#endif
3、hello.c / hello.h
#include "hello.h"
void print_hello(void)
{
printf("hello word!\n");
}
#ifndef __HELLO_H__
#define __HELLO_H__
#include <stdio.h>
void print_hello(void);
#endif
2. Use gcc to generate a static library
1. Generate the corresponding .o file
gcc -c hello.c
生成对应的.o文件
gcc -c sub.c
ls -l查看该目录下文件，看是否成功
2. Generate the corresponding .a file
ar -crv libmyhello.a hello.o
ar -crv libmysub.a sub.o
ls -l
3. Connect the static library to run the function
gcc main.c libmyhello.a sub.a -o main
./main
3. Use gcc to generate a dynamic library
1. Generate .so file
gcc -shared -fPIC -o libhello.so hello.o
gcc -shared -fPIC -o libsub.so sub.o
ls -l
2. Use the dynamic library to run the program
注意！！
When using the dynamic library, the program looks for the dynamic library under /usr/lib, and the dynamic library must be copied to this directory first
mv libhello.so /usr/lib
mv lib sub.so /usr/lib
gcc -o hello main.c -L. -lhello -lsub
ls -l
./main
Summarize
By practicing the generation and use of dynamic libraries/static libraries under gcc, I realized the charm of Linux and benefited a lot!