> 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/pthread/pthread_setspecific.3.md).

# pthread\_setspecific.3

`pthread_setspecific` — 设置线程特定数据值

## 名称

`pthread_setspecific`

## 库

libpthread

## 概要

```c
#include <pthread.h>

int
pthread_setspecific(pthread_key_t key, const void *value)
```

## 描述

`pthread_setspecific` 函数将线程特定值与先前通过调用 `pthread_key_create` 获取的 `key` 关联。不同线程可以将不同的值绑定到同一个键。这些值通常是指向为调用线程保留使用的动态分配内存块的指针。

使用非 `pthread_key_create` 获取的键值调用 `pthread_setspecific`，或在 `key` 已被 `pthread_key_delete` 删除后调用，其效果未定义。

`pthread_setspecific` 函数可以从线程特定数据析构函数中调用，但如果这样做导致在 `PTHREAD_DESTRUCTOR_ITERATIONS` 次析构函数调用后仍有非 NULL 的键值残留，可能导致存储丢失或无限循环。

## 返回值

如果成功，`pthread_setspecific` 函数将返回零。否则将返回一个错误号以指示错误。

## 错误

`pthread_setspecific` 函数将在以下情况失败：

**`[ENOMEM]`** 内存不足，无法将值与 `key` 关联。

**`[EINVAL]`** `key` 的值无效。

## 参见

[pthread\_getspecific(3)](https://github.com/FreeBSD-Ask/freebsd-man-sc/blob/main/man3/pthread_getspecific.3.md), [pthread\_key\_create(3)](https://github.com/FreeBSD-Ask/freebsd-man-sc/blob/main/man3/pthread_key_create.3.md), [pthread\_key\_delete(3)](https://github.com/FreeBSD-Ask/freebsd-man-sc/blob/main/man3/pthread_key_delete.3.md)

## 标准

`pthread_setspecific` 函数符合 ISO/IEC 9945-1:1996 ("POSIX.1") 规范。


---

# 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/pthread/pthread_setspecific.3.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.