TCSETSID(3)

💖 TCSETSID(3) 💖

okay so bestie, this is a page from the Library Functions Manual, and it’s about a lil function that hooks a session up to a controlling terminal. slay, but with rules. 💅

✨ NAME ✨

tcsetsid — set session ID associated with a controlling terminal 🫶

🌸 LIBRARY 🌸

Standard C Library (libc, -lc) 🎀

🦋 SYNOPSIS 🦋

#include <termios.h>

int
tcsetsid(int fd, pid_t pid);

🌈 DESCRIPTION 🌈

okay so tcsetsid() associates a session identified by pid with a controlling terminal specified by fd. that’s the whole vibe. ✨

but here’s the catch, and it’s kind of a big one: this implementation only allows the controlling terminal to be changed by the session leader itself. which means pid always has to be equal to the process ID. no cap. 👑

also, it is unsupported to associate with a terminal that already has an associated session. and conversely, it is also unsupported to associate to a terminal when the session is already associated with a different terminal. so yeah, no messy love triangles between sessions and terminals. 💀

💅 ERRORS 💅

if something goes wrong, tcsetsid() returns -1 and the global variable errno is set to indicate the error, as follows:

• [EBADF] — the fd argument is not a valid file descriptor. 🙈
• [ENOTTY] — the file descriptor represented by fd is not a terminal. 😭
• [EINVAL] — the pid argument is not equal to the session ID of the calling process. ⭐
• [EPERM] — the calling process is not a session leader. 🫠
• [EPERM] — the session already has an associated terminal, or the terminal already has an associated session. 💀

👑 SEE ALSO 👑

getsid(2), setsid(2), tcgetpgrp(3), tcgetsid(3) 🦋

🎀 HISTORY 🎀

a tcsetsid() function first appeared in QNX. it does not comply to any standard. iconic behavior, honestly. 💖

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mwah 💋 — this page is from Debian, dated November 28, 2022, and it’s the TCSETSID(3) manual page. 🍓