# 5.11. gethostname()－我是誰？

比 getpeername() 更簡單的函式是 gethostname()，它會傳回你執行程式的電腦名稱，這個名稱之後可以用在 gethostbyname()，用來定義你本機電腦的 IP address。

有什麼更有趣的嗎？

我可以想到一些事情，不過這不適合 socket 程式設計，總之，下面是一段範例：

```c
#include <unistd.h>
int gethostname(char *hostname, size_t size);
```

參數很簡單：hostname 是指向字元陣列（array of chars）的指標，它會儲存函式傳回的主機名稱（hostname），而 size 是以 byte 為單位的主機名稱長度。

函式在成功執行時傳回 0，在錯誤時傳回 -1，並一樣設定 errno。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://beej.netdpi.net/05-system-call-or-bust/5gethostname.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.