shutdown(2)

💅 shutdown — the bestie who knows when to say bye

Okay so shutdown(2) is a system call, she lives in the System Calls Manual, and she's the one who handles the ✨goodbye✨ part of a full-duplex connection. Not the whole vibe — just part of it. We love a queen who knows her lane. 🎀

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🌸 LIBRARY

Standard C library (libc, -lc) — she's already in the building, bestie, no extra linking needed.

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✨ SYNOPSIS

#include <sys/socket.h>

int shutdown(int sockfd, int how);

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🦋 DESCRIPTION

So like, the shutdown() call causes all or part of a full-duplex connection on the socket associated with sockfd to be shut down. Choose your fighter:

• If how is SHUT_RD → further receptions will be disallowed. No more incoming, periodt. 🙅‍♀️
• If how is SHUT_WR → further transmissions will be disallowed. You can still hear them, you just can't talk back. It's giving ✨boundaries✨.
• If how is SHUT_RDWR → further receptions and transmissions will be disallowed. Full send on the goodbye. Both directions, gone, iconic. 💀

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💖 RETURN VALUE

• On success, zero is returned. Queen behavior. 👑
• On error, -1 is returned, and errno is set to indicate the error. Rude of her but okay. 😭

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🔥 ERRORS

• EBADF — sockfd is not a valid file descriptor. Not a real fd, not a real one of us, we don't know her. 🚫
• EINVAL — An invalid value was specified in how (but see BUGS below, it's a whole situation).
• ENOTCONN — The specified socket is not connected. Ma'am, there's no connection, what are we even shutting down? 🙈
• ENOTSOCK — The file descriptor sockfd does not refer to a socket. Bestie that's not a socket, that's just… a file. 🌵

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📜 STANDARDS

POSIX.1-2024. Certified. 📋

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🕰️ HISTORY

POSIX.1-2001, 4.4BSD (first appeared in 4.2BSD). She's old money, been doing this since the 4.2BSD era. Vintage but still relevant, we stan a timeless icon. ⭐

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🧚 NOTES

The constants SHUT_RD, SHUT_WR, and SHUT_RDWR have the value 0, 1, and 2, respectively — in that order, no cap — and they're defined in <sys/socket.h> since glibc-2.1.91. So like, they've been living there for a minute. 💅

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🐛 BUGS

Okay so lowkey a cautionary tale, listen up:

Checks for the validity of how are done in domain-specific code, and before Linux 3.7 not all domains performed these checks. Most notably, UNⅨ domain sockets just… simply ignored invalid values. Like, straight up didn't care, no vibe check, nothing. 😭

This problem was fixed for UNIX domain sockets in Linux 3.7. So if you're on something ancient, bestie, watch yourself. 🫶

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👀 SEE ALSO

close(2), connect(2), socket(2), socket(7) — the whole friend group, go read them too, iykyk. 🍓

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tl;dr: you want to half-close a socket? shutdown() is your girl. You want to fully destroy it? That's a close(2) conversation, different bestie, different energy. 💖

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This little love letter comes to you courtesy of Linux man-pages 6.20, dated 2025-10-29. Mwah, go close your sockets responsibly. ✨🦋💅