https://blog.gongquiz.com/2022/05/14/unix%ec%97%90%ec%84%9c-%ed%98%84%ec%9e%ac-%ec%9e%91%ec%97%85%ec%a4%91%ec%9d%b8-%eb%94%94%eb%a0%89%ed%86%a0%eb%a6%ac%ec%9d%98-%eb%aa%a8%eb%93%a0-%ed%8c%8c%ec%9d%bc%ec%9d%84-%eb%b3%b4%ec%97%ac%ec%a3%bc/