> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/man/man9/device_printf.9.md).

# device\_printf.9

`device_printf` — 格式化输出转换

## 名称

`device_printf`

## 概要

```c
#include <sys/param.h>
#include <sys/bus.h>

int
device_printf(device_t dev, const char *fmt, ...);
```

## 描述

`device_printf` 函数是 [printf(9)](/man/man9/printf.9.md) 函数的便捷接口。它先输出 `dev` 设备的名称，后跟一个冒号和一个空格，然后输出将 `fmt` 及其余参数传递给 [printf(9)](/man/man9/printf.9.md) 时所会打印的内容。

## 返回值

`device_printf` 函数返回显示的字符数。

## 参见

[printf(3)](https://github.com/FreeBSD-Ask/freebsd-man-sc/tree/main/man3/printf.3.md), [printf(9)](/man/man9/printf.9.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## 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, and the optional `goal` query parameter:

```
GET https://book.bsdcn.org/man/man9/device_printf.9.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

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.