# 非标准库unistd.h

unistd.h为Linux/Unix系统中内置头文件，包含了许多系统服务的函数原型，例如read函数、write函数和getpid函数等。
其作用相当于windows操作系统的"windows.h"，是操作系统为用户提供的统一API接口，方便调用系统提供的一些服务。

## 常用

### sleep()函数

系统延时函数，接受参数为秒。
<!-- markdown for nginx, see https://phus.lu -->
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