strstr(3)

✨ strstr(3) ✨

okay bestie, so this is strstr(3) from the Library Functions Manual, and it's literally the "find my substring" function. she's simple, she's iconic, she's been holding down C string searching since forever 💖 let's get into it

---

🎀 NAME 🎀

strstr — string search substring

like. the name says it all. string, search, substring. no cap.

---

🏛️ LIBRARY 🏛️

Standard C library (libc, -lc)

the one and only. she's built in, she's always there for you 🫶

---

🌸 SYNOPSIS 🌸

#include <string.h>

char *strstr(const char *haystack, const char *needle);

yes you have to #include <string.h> first, don't be that girl who forgets the include 🙈

---

💅 DESCRIPTION 💅

so strstr() finds the first occurrence of the substring needle in the string haystack. it's giving "you dropped this needle in a haystack and I found it immediately, you're welcome" 🔥

the terminating null bytes ('\0') are not compared. nope. not part of the vibe. those two little terminators get to sit this one out 💀

it is equivalent to

memmem(haystack, strlen(haystack), needle, strlen(needle))

so if you already knew memmem, you basically already knew this. academic besties fr fr ✨

---

🦋 RETURN VALUE 🦋

strstr(3) returns a pointer to the beginning of the located substring, or NULL if the substring is not found. no substring, no pointer, no crumbs. NULL is the ghosting 💀

but wait — plot twist — if needle is the empty string, the return value is always haystack itself. she's already there. she never left. periodt. 👑

---

🌈 ATTRIBUTES 🌈

for an explanation of the terms used in this section, see attributes(7). here's the vibe check:

• strstr() — Thread safety: MT-Safe 🎀

MT-Safe means she plays nice with all your threads, no drama, no fighting, we love a peaceful queen 💖

---

⭐ STANDARDS ⭐

C11, POSIX.1-2008.

certified. standardized. official. the committee said slay and she ate 🔥

---

👑 HISTORY 👑

POSIX.1-2001, C89.

she's been here since C89, bestie. ancient. timeless. a true main character who predates most of your faves 🌸

---

🧚 SEE ALSO 🧚

• strcasestr(3)
• strchr(3)
• string(3)
• strpbrk(3)
• strsep(3)
• strspn(3)
• wcsstr(3)

go read those too, they're all part of the same friend group 🫶

---

okay that's the whole page!! 💜 this was brought to you by Linux man-pages 6.20, dated 2026-08-10, and written by the strstr(3) girlies. now go find your substring, you've got this ✨🎀💖