TIOCSLCKTRMIOS(2const)

✨ NAME ✨

TIOCGLCKTRMIOS, TIOCSLCKTRMIOS — locking the termios structre 💅

(no bestie that's not a typo I made, that's the typo the page itself is serving, we're keeping it, it's part of the lore now 🫶)

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📚 LIBRARY 📚

Standard C library (libc, -lc)

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🧚 SYNOPSIS 🧚

#include <asm/termbits.h>  /* Definition of TIOC*CLKTRMIOS constants */
#include <sys/ioctl.h>

int ioctl(int fd, TIOCGLCKTRMIOS, struct termios *argp);
int ioctl(int fd, TIOCSLCKTRMIOS, const struct termios *argp);

#include <asm/termbits.h>

struct termios;

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🌸 DESCRIPTION 🌸

Okay so picture this: a terminal has a termios structure, right? And that structure can be locked 🔒. The lock is itself a termios structure too — and any nonzero bit or field in it means "this value is locked, do not touch, it's giving off-limits energy".

• TIOCGLCKTRMIOS — gets the locking status of the termios structure of the terminal. Basically: "hey bestie, what's locked rn?" 👀
• TIOCSLCKTRMIOS — sets the locking status of the termios structure of the terminal. And lowkey important: only a process with the CAP_SYS_ADMIN capability can do this. That's a whole admin key, not a vibe you can just walk in with. 👑

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🎀 RETURN VALUE 🎀

• Success? 0 is returned. Iconic. ✨
• Error? -1 is returned, and errno gets set to tell you what went wrong. 💀

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🦋 ERRORS 🦋

• EPERM — insufficient permission. You simply do not have the range, bestie. 🙈

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💀 CAVEATS 💀

Please note that struct termios from <asm/termbits.h> is different and incompatible with struct termios from <termios.h>.

Not "kind of different". Incompatible. These two are not the same struct and they are not interchangeable, no cap. And these ioctl calls require struct termios from <asm/termbits.h>. Use the wrong one and you'll be staring at your screen like 😭. The right include is the <asm/termbits.h> one, periodt. 💖

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👑 SEE ALSO 👑

• ioctl(2)
• ioctl_tty(2)
• TCSETS(2const)

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that's the whole page bestie, go lock some termios (with CAP_SYS_ADMIN tho, fr fr) 🌈

sourced from Linux man-pages 6.20, dated 2026-02-08 — cute little timestamp, keep it in your notes 💜