venv 是 Python3.3 以后的功能，官方文档在此。

GitHub: mmdjiji/cmake-learning

Introduction

After I learned how to write makefile, I found that this was not enough to enable me to build all projects, such as KDE, OpenCV and so on. So I determined to learn CMake, an awesome building tool, which can be use on all platforms. You can download CMake by this page.

GitHub: mmdjiji/makefile-learning.

Introduction

What is makefile? Most Windows developers don’t know this, and it is useful in Linux development. Most often, the makefile directs Make on how to compile and link a program.

扫描集

扫描集为一个字符集合，用来匹配期待输入的字符。对于scanf匹配输入内容时，可以使用扫描集灵活地进行字符串截取输入。

扫描集以 % 开头，用 [] 包含字符集。如扫描集 %[abc], %[a-z], %[^abc], %[^a-z] ，其中 ^ 表示求反集。

在阅读文章前，请先思考下面的代码执行结果是什么：

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#include <stdio.h>
int main(){
  struct{
    int x; int y;
  }s[2] = {{2, 0}, {1, 3}}, *p = s;
  printf("%d, %d", ++p->x, (++p)->x);
  return 0;
}