TIOCSWINSZ(2const)

✨ TIOCGWINSZ, TIOCSWINSZ ✨

okay bestie so you found yourself in the TIOCSWINSZ section of the 2const manual, and honestly? it's giving window resize energy 💅 this is the get-and-set-window-size duo.

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🫶 LIBRARY

Standard C library (libc, -lc) — the classic, the icon, no cap.

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🌸 SYNOPSIS

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

int ioctl(int fd, TIOCGWINSZ, struct winsize *argp);
int ioctl(int fd, TIOCSWINSZ, const struct winsize *argp);

#include <asm/termios.h>

struct winsize {
    unsigned short ws_row;
    unsigned short ws_col;
    unsigned short ws_xpixel;  /* unused */
    unsigned short ws_ypixel;  /* unused */
};

so you're calling ioctl() with one of two constants and handing it a pointer to a struct winsize. TIOCGWINSZ gets, TIOCSWINSZ sets. and yeah, the header for the constants is asm/termbits.h, but the struct lives over in asm/termios.h, so you need both. annoying? yes. iconic? also yes 😭

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💖 DESCRIPTION

The window sizes are kept in the kernel, but — plot twist — the kernel doesn't actually use them. lowkey the kernel is just holding them for you like a supportive bestie holding your bag 👜

exception: virtual consoles. In that one case, the kernel will update the window size when the size of the virtual console changes — for example, by loading a new font. so if fonts are your thing, this matters, otherwise it's vibes only.

TIOCGWINSZ Goal: get window size. 📏

TIOCSWINSZ Goal: set window size. ✍️

and when the window size changes, a SIGWINCH signal gets sent to the foreground process group. that's right, your terminal is literally sending a signal, main character behavior, it just wants to tell you the shape of things changed 🔥

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⭐ RETURN VALUE

On success, 0 is returned. On error, -1 is returned, and errno is set to indicate the error. so check your errno, bestie, it's not gonna text you first 💀

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👑 SEE ALSO

• ioctl(2)
• ioctl_tty(2const)

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mwah, that's the whole page, no filler, no fluff, fr fr 🦋 this came from Linux man-pages 6.20, dated 2026-02-08 — go off, go resize something, periodt 💅✨