SHUTDOWN(2)

✨ shutdown(2) ✨

okay so bestie, welcome to shutdown(2) — the System Calls Manual page you didn't know you needed 💅 no cap.

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🌸 NAME 🌸

shutdown — disable sends and/or receives on a socket 🚫📤📥

📚 LIBRARY 📚

Standard C Library (libc, -lc) 🫶

✨ SYNOPSIS ✨

#include <sys/types.h>
#include <sys/socket.h>

int
shutdown(int s, int how);

💖 DESCRIPTION 💖

The shutdown() system call disables sends or receives on a socket. Like, it's giving "we're done here" energy to one direction or both 🎀

The how argument specifies the type of shutdown. Possible values are:

• SHUT_RD — further receives will be disallowed. bye bye incoming data 💌
• SHUT_WR — further sends will be disallowed. This may cause actions specific to the protocol family of the socket s to happen; see “IMPLEMENTATION NOTES”. lowkey this one has side quests 👀
• SHUT_RDWR — further sends and receives will be disallowed. Implies SHUT_WR. both directions? gone. periodt.

If the file descriptor s is associated with a SOCK_STREAM socket, all or part of the full-duplex connection will be shut down. iconic behavior honestly 🌈

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🧚 IMPLEMENTATION NOTES 🧚

The following protocol specific actions apply to the use of SHUT_WR (and potentially also SHUT_RDWR), based on the properties of the socket associated with the file descriptor s.

Like, the vibe check depends on your domain + type + protocol combo, so here's the whole roster 🦋:

• Domain PF_INET, Type SOCK_DGRAM, Protocol IPPROTO_SCTP — failure, as socket is not connected. 💀
• Domain PF_INET, Type SOCK_DGRAM, Protocol IPPROTO_UDP — failure, as socket is not connected. 💀
• Domain PF_INET, Type SOCK_STREAM, Protocol IPPROTO_SCTP — send queued data and tear down association. 🔥
• Domain PF_INET, Type SOCK_STREAM, Protocol IPPROTO_TCP — send queued data, wait for ACK, then send FIN. 🔥
• Domain PF_INET6, Type SOCK_DGRAM, Protocol IPPROTO_SCTP — failure, as socket is not connected. 💀
• Domain PF_INET6, Type SOCK_DGRAM, Protocol IPPROTO_UDP — failure, as socket is not connected. 💀
• Domain PF_INET6, Type SOCK_STREAM, Protocol IPPROTO_SCTP — send queued data and tear down association. 🔥
• Domain PF_INET6, Type SOCK_STREAM, Protocol IPPROTO_TCP — send queued data, wait for ACK, then send FIN. 🔥

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👑 RETURN VALUES 👑

The shutdown() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

so: 0 = slay, -1 = the group chat has bad news and errno is the receipts 📱

😭 ERRORS 😭

The shutdown() system call fails if:

• EBADF — the s argument is not a valid file descriptor. 🚩
• EINVAL — the how argument is invalid. 🚩
• ENOTCONN — the s argument specifies a socket which is not connected. 🚩
• ENOTSOCK — the s argument does not refer to a socket. 🚩

bestie not every one of these is your fault but every one of these means you're not getting what you wanted 🙈

🌈 SEE ALSO 🌈

connect(2), socket(2), inet(4), inet6(4)

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⭐ STANDARDS ⭐

The shutdown() system call is expected to comply with IEEE Std 1003.1g-2000 (“POSIX.1”), when finalized. pending finalization, we wait 🫶

🎀 HISTORY 🎀

The shutdown() system call appeared in 4.2BSD. The SHUT_RD, SHUT_WR, and SHUT_RDWR constants appeared in IEEE Std 1003.1g-2000 (“POSIX.1”). a legacy icon fr fr 👑

💜 AUTHORS 💜

This manual page was updated by Bruce M. Simpson <bms@FreeBSD.org> to reflect how shutdown() behaves with PF_INET and PF_INET6 sockets. thank you for your service 🫡💖

💀 BUGS 💀

The ICMP “port unreachable” message should be generated in response to datagrams received on a local port to which s is bound after shutdown() is called.

ngl that one's just... not happening when it should 😭 noted, not fixed.

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and that's the whole page bestie 💅 this one's from the Debian crew, dated July 27, 2015 — go forth and close your sockets responsibly ✨