diff --git a/day8/d2/README.md b/day8/d2/README.md
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+### 动态库 (libxx.so) 生成
+
+```bash
+# 生成 xx 工具的动态库 xx.c ---> libxx.so
+gcc -shared xx.c -o libxx.so
+```
+
+### 静态库的使用
+
+```bash
+# test.c 使用 libxx.so 编译生成可执行文件 test 的方式
+gcc test.c libxx.so -o test
+# 运行时需要将库文件的目录 (./是当前路径) 添加到 LD_LIBRARY_PATH 环境变量中
+export LD_LIBRARY_PATH=./my/libs:$LD_LIBRARY_PATH
+# 或者将生成的库文件和相关头文件添加 (或使用软连接) 到系统的库目录 (/usr/lib) 及系统的头文件目录 (/usr/include)中
+# 以 root 进入 /usr/lib 目录，然后创建软连接
+ln -s /动态库目录.../libxx.so .
+```
diff --git a/day8/d2/my.c b/day8/d2/my.c
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+++ b/day8/d2/my.c
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+#include "./my/includes/my.h"
+
+int sum(int a, int b)
+{
+    return a + b;
+}
+
+int sub(int a, int b)
+{
+    return a - b;
+}
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diff --git a/day8/d2/my/includes/my.h b/day8/d2/my/includes/my.h
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+++ b/day8/d2/my/includes/my.h
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+#ifndef __MY_H__
+#define __MY_H__
+
+#include <stdio.h>
+
+int sum(int, int);
+int sub(int, int);
+
+#endif
\ No newline at end of file
diff --git a/day8/d2/my/libs/libmy.so b/day8/d2/my/libs/libmy.so
new file mode 100755
index 0000000..b03c480
Binary files /dev/null and b/day8/d2/my/libs/libmy.so differ
diff --git a/day8/d2/test.c b/day8/d2/test.c
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+++ b/day8/d2/test.c
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+#include "./my/includes/my.h"
+
+int main()
+{
+    int a = 10, b = 20;
+    printf("10+20=%d\n", sum(a, b));
+    printf("20-10=%d\n", sub(b, a));
+    return 0;
+}
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