---
name: "pthread_self"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/pthread_self"
---

# pthread\_self(3)

obtain ID of the calling thread

## NAME

pthread\_self - obtain ID of the calling thread

## LIBRARY

POSIX threads library (*libpthread*, *-lpthread*)

## SYNOPSIS

```
#include <pthread.h>
```

**pthread\_t pthread\_self(void);**

## DESCRIPTION

The **pthread\_self**() function returns the ID of the calling thread. This is the same value that is returned in *\*thread* in the [**pthread\_create**(3)](/pthread_create/3.md) call that created this thread.

## RETURN VALUE

This function always succeeds, returning the calling thread's ID.

## ERRORS

This function always succeeds.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **pthread\_self**() | Thread safety | MT-Safe |

## STANDARDS

POSIX.1-2008.

## HISTORY

POSIX.1-2001.

## NOTES

POSIX.1 allows an implementation wide freedom in choosing the type used to represent a thread ID; for example, representation using either an arithmetic type or a structure is permitted. Therefore, variables of type *pthread\_t* can't portably be compared using the C equality operator (**==**); use [**pthread\_equal**(3)](/pthread_equal/3.md) instead.

Thread identifiers should be considered opaque: any attempt to use a thread ID other than in pthreads calls is nonportable and can lead to unspecified results.

Thread IDs are guaranteed to be unique only within a process. A thread ID may be reused after a terminated thread has been joined, or a detached thread has terminated.

The thread ID returned by **pthread\_self**() is not the same thing as the kernel thread ID returned by a call to [**gettid**(2)](/gettid/2.md).

## SEE ALSO

[**pthread\_create**(3)](/pthread_create/3.md), [**pthread\_equal**(3)](/pthread_equal/3.md), [**pthreads**(7)](/pthreads/7.md)