pthread_self(3)

✨ pthread_self(3) ✨

okay so bestie, we're in the Library Functions Manual today and the vibe is: your thread, but make it identity. this is pthread_self(3), and it's lowkey one of the most useful little calls in the whole pthreads situation. 💅

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💖 NAME 💖

pthread_self — obtain ID of the calling thread

so like. it gets you the ID of whichever thread is calling it. that's it. that's the function. 🎀

📚 LIBRARY 📚

POSIX threads library (libpthread, -lpthread)

(link against it or she simply will not run, no cap 🫶)

✨ SYNOPSIS ✨

#include <pthread.h>

pthread_t pthread_self(void);

🌸 DESCRIPTION 🌸

The pthread_self() function returns the ID of the calling thread. 💖

and here's the tea: this is the same value that was returned in *thread in the pthread_create(3) call that created this thread. so it's giving "who am i, really?" and the answer is literally the same answer you got when you were born into this process. iconic. 👑

🦋 RETURN VALUE 🦋

This function always succeeds, returning the calling thread's ID. like, she has never once failed. she doesn't know how. 💅

💀 ERRORS 💀

This function always succeeds.

that's it. that's the whole section. no error codes, no errno drama, nothing. not me reading a section that's just one sentence 😭

🎀 ATTRIBUTES 🎀

for an explanation of the terms used in this section, see attributes(7). 🌈

• Interface: pthread_self()
• Attribute: Thread safety
• Value: MT-Safe 🫶

👑 STANDARDS 👑

POSIX.1-2008. ✨

🕰️ HISTORY 🕰️

POSIX.1-2001. so she's been around. a legend, fr fr. ⭐

💜 NOTES 💜

okay this is the part where you actually pay attention, bestie, because there's real lore here:

• 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. 🙈 so the type could literally be anything.
• therefore, variables of type pthread_t can't portably be compared using the C equality operator (==); use pthread_equal(3) instead. do not be out here doing if (a == b), that's not it. use the function. periodt. 💅
• 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. like, don't peek behind the curtain. there's nothing for you back there. 🔥
• Thread IDs are guaranteed to be unique only within a process. and even then — a thread ID may be reused after a terminated thread has been joined, or a detached thread has terminated. so no clutching onto an old ID like it's yours forever. it's giving "ex, but make it a resource identifier." 💀
• The thread ID returned by pthread_self() is not the same thing as the kernel thread ID returned by a call to gettid(2). two completely different girls. don't confuse them. 🙅♀️

fr fr: opaque means opaque. compare with pthread_equal(3), don't compare with ==. 🎀

🔍 SEE ALSO 🔍

• pthread_create(3)
• pthread_equal(3)
• pthreads(7)

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and that's the whole page, bestie!! 🦋🌷💖 this was Linux man-pages 6.20, dated 2025-05-17 — shoutout to the man-pages girlies for keeping us fed, mwah. now go run pthread_equal(3) instead of == and slay responsibly. ✨👑💅