pthread_setname_np(3)

💖 pthread_setname_np(3) — the manual page, but make it cute 💖

okay bestie, gather round, because today we're talking about pthread_setname_np and pthread_getname_np from the pthread_setname_np(3) manual page — yes the whole page, no skips, we're doing this properly. it's giving "naming your threads so your debugger doesn't look like a hostage situation" energy and honestly? iconic. 🧵✨

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🌸 NAME 🌸

pthread_setname_np, pthread_getname_np — set/get the name of a thread 🏷️

📚 LIBRARY 📚

POSIX threads library (libpthread, -lpthread) 🫶

✨ SYNOPSIS ✨

#define _GNU_SOURCE             /* See feature_test_macros(7) */
#include <pthread.h>

int pthread_setname_np(pthread_t thread, const char *name);
int pthread_getname_np(size_t size;
                       pthread_t thread, char name[size], size_t size);

yes bestie the second declaration looks like that in the source, we do not fix it, we reproduce it, that's the rule 💅

💅 DESCRIPTION 💅

so. by default, every single thread you make with pthread_create() just inherits the program name. every one. all of them. same name. chaos. 💀

enter pthread_setname_np() — it lets you give a thread its own unique name, which is lowkey invaluable when you're debugging multithreaded apps and you need to know which thread did the crime. 🔍

the thread name is a meaningful C language string, and its length is restricted to 16 characters, including the terminating null byte ('\0'). so 15 visible chars, bestie, that's the budget, spend it wisely. 🎀

• the thread argument says which thread's name you're changing
• name is the new name, periodt

and pthread_getname_np()? that's the reverse girlypop — it retrieves a thread's name. 🪞

• thread specifies the thread whose name you want
• the buffer name is what the thread name gets returned in
• size is how many bytes are available in name
• the buffer given by name should be at least 16 characters in length
• the returned thread name in the output buffer will be null terminated

no cap, 16 chars. that's the vibe check. ⭐

🔥 RETURN VALUE 🔥

• on success, these functions return 0 ✅
• on error, they return a nonzero error number ❌

😭 ERRORS 😭

pthread_setname_np() can fail with this one:

• ERANGE — the length of the string pointed to by name exceeds the allowed limit. too long bestie, it said 16, it meant 16. 🚫

pthread_getname_np() can fail with this one:

• ERANGE — the buffer specified by name and size is too small to hold the thread name. tiny buffer, big name energy, and not in a good way. 🙈

also, if either of these functions fails to open /proc/self/task/tid/comm, then the call may fail with one of the errors described in open(2). so like, it's not always about the name, sometimes the filesystem is just having a day. 🌀

🫶 ATTRIBUTES 🫶

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

• Interface: pthread_setname_np(), pthread_getname_np()
• Attribute: Thread safety
• Value: MT-Safe

slay, they're thread safe, we love a function that doesn't betray you. 👑

👑 STANDARDS 👑

GNU — hence the suffix "_np" (nonportable) in the names. so like, it works here, but don't go assuming every libc is gonna hold your hand. iykyk. 🌈

🦋 HISTORY 🦋

glibc 2.12. blast from the past, but a good one. 💜

📝 NOTES 📝

• pthread_setname_np() internally writes to the thread-specific comm file under the /proc filesystem: /proc/self/task/tid/comm
• pthread_getname_np() retrieves it from the same location

secretly it's all just files, bestie, it's always files. 🍓

🎀 EXAMPLES 🎀

the program below demonstrates the use of pthread_setname_np() and pthread_getname_np().

and here's a sample run of the program from a shell session:

$ ./a.out;
Created a thread.  Default name is: a.out
The thread name after setting it is THREADFOO.
^Z                           # Suspend the program
[1]+  Stopped           ./a.out
$ ps H -C a.out -o 'pid tid cmd comm'
  PID   TID CMD                         COMMAND
 5990  5990 ./a.out                     a.out
 5990  5991 ./a.out                     THREADFOO
$ cat /proc/5990/task/5990/comm
a.out
$ cat /proc/5990/task/5991/comm
THREADFOO

look at those two cat calls proving the whole thing. the comm file said what it said. 😌

🌸 Program source 🌸

#define _GNU_SOURCE
#include <err.h>
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define NAMELEN 16

static void *
threadfunc(void *parm)
{
    sleep(5);          // allow main program to set the thread name
    return NULL;
}

int
main(int argc, char *argv[])
{
    pthread_t thread;
    int rc;
    char thread_name[NAMELEN];

    rc = pthread_create(&thread, NULL, threadfunc, NULL);
    if (rc != 0)
        errc(EXIT_FAILURE, rc, "pthread_create");

    rc = pthread_getname_np(thread, thread_name, NAMELEN);
    if (rc != 0)
        errc(EXIT_FAILURE, rc, "pthread_getname_np");

    printf("Created a thread.  Default name is: %s\n", thread_name);
    rc = pthread_setname_np(thread, (argc > 1) ? argv[1] : "THREADFOO");
    if (rc != 0)
        errc(EXIT_FAILURE, rc, "pthread_setname_np");

    sleep(2);

    rc = pthread_getname_np(thread, thread_name, NAMELEN);
    if (rc != 0)
        errc(EXIT_FAILURE, rc, "pthread_getname_np");
    printf("The thread name after setting it is %s.\n", thread_name);

    rc = pthread_join(thread, NULL);
    if (rc != 0)
        errc(EXIT_FAILURE, rc, "pthread_join");

    printf("Done\n");
    exit(EXIT_SUCCESS);
}

copy it, run it, NAMELEN 16 is right there doing the lord's work. 🔥

💜 SEE ALSO 💜

• prctl(2)
• pthread_create(3)
• pthreads(7)

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that's the whole page bestie, every flag, every error, every byte of that hex-free 16-char limit. go forth and name your threads something cute. 🦋💖

sign-off time: this lil treasure came from Linux man-pages 6.20 and it's dated 2026-02-08. 🎀 thanks for reading, ily, now go pthread_join something before it leaks. 💅✨