ctermid(3)

✨ ctermid(3) ✨

okay bestie, welcome to the ctermid(3) page, straight out of the Library Functions Manual 💖 this one lives in the Standard C library (libc, -lc) and it's literally a lil function that tells you the pathname of your controlling terminal. so cozy. so simple. let's get into it 🫶

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🌸 NAME 🌸

ctermid — get controlling terminal name

📚 LIBRARY 📚

Standard C library (libc, -lc)

🎀 SYNOPSIS 🎀

#include <stdio.h>

char *ctermid(char *s);

✨ Feature Test Macro Requirements for glibc (see feature_test_macros(7)) ✨

• ctermid(): _POSIX_C_SOURCE

💅 DESCRIPTION 💅

so ctermid() hands you back a string, and that string is the pathname for the current controlling terminal of this process. that's the whole vibe. 👑

now here's the tea on the s argument:

• if s is NULL, a static buffer gets used instead — you don't bring your own storage, the function just has one chilling there.
• otherwise, s points to a buffer that you're providing, and that buffer is what holds the terminal pathname.

and a lil icon that you need to know: the symbolic constant L_ctermid is the maximum number of characters in the returned pathname. it's giving "know your buffer size, bestie" 📏✨

🔥 RETURN VALUE 🔥

The pointer to the pathname. that's it. that's the return. 💖

👑 ATTRIBUTES 👑

for an explanation of the terms used in this here section, go peek at attributes(7).

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

translation? she's MT-Safe, she's fine in threads, no drama 🌈

⭐ STANDARDS ⭐

POSIX.1-2008. periodt.

🦋 HISTORY 🦋

POSIX.1-2001, Svr4. she's been around a minute, no cap.

💀 BUGS 💀

okay bestie, warning time, listen up:

The returned pathname may not uniquely identify the controlling terminal; it may, for example, be /dev/tty.

It is not assured that the program can open the terminal.

so like… the string you get back is lowkey vibes-only, it does not guarantee you can actually open the thing. do not come for me about it, I'm just the messenger 😭🙈

🌸 SEE ALSO 🌸

• ttyname(3)

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and that's the page, bestie!! 🎀 go forth and get your controlling terminal name responsibly 💖 this was Linux man-pages 6.20, dated 2026-02-08 — mwah, love u, bye 👑✨