strdup(3)

💖 strdup(3) — string duplicate 💖

okay bestie, so you know how you have a string and you do not wanna mess with the original? yeah. this is that. it's strdup from the Library Functions Manual, and it's literally the moment your string gets a twin. 👯‍♀️✨

📚 LIBRARY

Standard C library (libc, -lc) — she lives in libc, no cap. 🫶

✨ SYNOPSIS ✨

#include <string.h>

char *strdup(const char *s);

🧚 Feature Test Macro Requirements for glibc 🧚

(if you wanna know the whole lore on these, go peek at feature_test_macros(7))

strdup():

_XOPEN_SOURCE >= 500
    || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
    || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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🌸 DESCRIPTION 🌸

The strdup() function hands you back a pointer to a brand new string that is a duplicate of the string s. like, a whole copy. its own whole vibe.

The memory for that new string? It's obtained with malloc(3), and you can free it with free(3). so yeah, it's yours, you own it, you have to clean it up. main character responsibilities. 👑

💀 bestie PLEASE — that memory came from malloc(3), so it is NOT free real estate. if you don't free(3) it, that's a leak. do not ghost your allocations.

🎀 RETURN VALUE 🎀

On success, strdup() returns a pointer to the duplicated string. iconique. ✨

It returns NULL if there wasn't enough memory available, with errno set to indicate the error. so yeah, check it. fr fr. 😭

🔥 ERRORS 🔥

See malloc(3). that's the whole section, she's brief but she's holding the receipts.

👑 ATTRIBUTES 👑

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

• Interface: strdup()
• Attribute: Thread safety
• Value: MT-Safe 🌈

(not me converting the table, the table is cute but the list is cuter 💅)

⭐ STANDARDS ⭐

POSIX.1-2008. certified, approved, periodt.

🦋 HISTORY 🦋

SVr4, 4.3BSD-Reno, POSIX.1-2001. she's been around. legacy queen behavior. 👑

🌈 SEE ALSO 🌈

malloc(3), string(3), strdupa(3), wcsdup(3)

the whole friend group, go say hi. 🫶

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Linux man-pages 6.20 · 2026-08-10 · strdup(3) — mwah, that's the page bestie, go duplicate responsibly and free your memory 💖✨🎀