# 基于文件描述符的I/O操作

文件描述符是Linux内核操作管理文件的一个索引值，由它来指定文件操作的对象。当某个进程打开一个现存文件或者创建一个新文件时，内核便向进程返回一个文件描述符。

* 文件描述 0 与进程的标准输入（standard input）相结合
* 文件描述 1 与进程的标准输出（standard output）相结合
* 文件描述 2 与进程的标准出错（standard error）相结合


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