GRANTPT(3POSIX)

📦 version 2017a, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

💅 GRANTPT(3POSIX) 💅

ok bestie so this one lives in the POSIX Programmer's Manual and it's literally called grantpt — lowercase, three-POSIX, the whole vibe. 🫶

📜 PROLOG

Real talk before we even start: this page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so go check the corresponding Linux manual page for the deets on Linux behavior), or the interface might not even be implemented on Linux at all. 💀 Just so you know.

✨ NAME ✨

grantpt — grant access to the slave pseudo-terminal device. That's it, that's the whole job. 👑

🌸 SYNOPSIS 🌸

#include <stdlib.h>

int grantpt(int fildes);

🦋 DESCRIPTION 🦋

Okay so here's what grantpt() actually does: it shall change the mode and ownership of the slave pseudo-terminal device that's associated with its master pseudo-terminal counterpart. Iconic behavior honestly.

The fildes argument is a file descriptor that refers to a master pseudo-terminal device. (Master, not slave — read it again, bestie, it matters.)

Then:

  • The user ID of the slave shall be set to the real UID of the calling process.
  • The group ID shall be set to an unspecified group ID. (Yes, unspecified. Don't come for me, that's what it says. 🙈)
  • The permission mode of the slave pseudo-terminal shall be set to readable and writable by the owner, and writable by the group.
⚠️ Heads up: the behavior of the grantpt() function is unspecified if the application has installed a signal handler to catch SIGCHLD signals. So like… don't do that. 💀

🎀 RETURN VALUE 🎀

  • On a successful completion, grantpt() shall return 0. slay. ✨
  • Otherwise, it shall return -1 and set errno to indicate the error. not slay. 😭

💅 ERRORS 💅

The grantpt() function may fail if:

  • EACCES — the corresponding slave pseudo-terminal device could not be accessed. it's giving locked out 🚪
  • EBADF — the fildes argument is not a valid open file descriptor. bestie that's not a real fd 💀
  • EINVAL — the fildes argument is not associated with a master pseudo-terminal device. wrong device, wrong vibe 🚫
📌 psst: the following sections are informative. (POSIX's way of saying "this part is extra, not requirements".)

🌈 EXAMPLES 🌈

None. 😌 nothing to show, the example section is empty, that's canon.

💜 APPLICATION USAGE 💜

None. 🙈 also empty. we love a low-effort section.

🧚 RATIONALE 🧚

See the RATIONALE section for posix_openpt(). That's where the lore lives, go read it. 📖

⭐ FUTURE DIRECTIONS ⭐

None. nothing on the horizon, no glow-up planned. 🌙

🔥 SEE ALSO 🔥

  • open()
  • posix_openpt()
  • ptsname()
  • unlockpt()

Also: The Base Definitions volume of POSIX.1‐2017, <stdlib.h>. 📚

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

and that's the whole page, bestie 💖 brought to you by IEEE/The Open Group, 2017 — yeah, 2017, she's vintage and she still ate. periodt. 🎀✨

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