sys_uio.h(7POSIX)

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

💖 PROLOG 💖

okay so real talk first, bestie — this manual page is part of the POSIX Programmer's Manual (yes, the sys_uio.h(7POSIX) one, we're doing the deep lore today 🫶). Important heads-up though: the Linux implementation of this interface may differ (so pls consult the corresponding Linux manual page for details of Linux behavior), or like… the interface might not even be implemented on Linux at all. 💀 so don't come for me if it's not there.

🌸 NAME 🌸

sys/uio.h — definitions for vector I/O operations ✨

🎀 SYNOPSIS 🎀

#include <sys/uio.h>

that's it, that's the whole vibe. so slay.

🦋 DESCRIPTION 🦋

okay so the <sys/uio.h> header shall define the iovec structure, and it shall include at least these members:

void   *iov_base  Base address of a memory region for input or output.
size_t  iov_len   The size of the memory pointed to by iov_base.

literally the blueprint. 🧚

The <sys/uio.h> header uses the iovec structure for scatter/gather I/O. that's the whole point bestie, it's giving gather girl energy.

The <sys/uio.h> header shall define the ssize_t and size_t types as described in <sys/types.h>. no cap.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

ssize_t readv(int, const struct iovec *, int);
ssize_t writev(int, const struct iovec *, int);
✨ note: the following sections are informative. so like, the vibes sections. still read them tho.

💅 APPLICATION USAGE 💅

okay so your implementation can put a limit on the number of scatter/gather elements it can process in one call. and the symbol {IOV_MAX} defined in <limits.h> should always be used to learn about the limits instead of assuming a fixed value. do NOT hardcode it, I'm begging 🙈 that's the number one way to get humbled.

🔥 RATIONALE 🔥

so back in the day, the maximum number of scatter/gather elements the system can process in one call was described by the symbolic value {UIO_MAXIOV}. in IEEE Std 1003.1‐2001 this value got replaced by the constant {IOV_MAX} which can be found in <limits.h>. glow up era. 👑

🌈 FUTURE DIRECTIONS 🌈

None.

(iconic honestly. nothing on the horizon. we rest. 😌)

⭐ SEE ALSO ⭐

  • <limits.h>
  • <sys_types.h>
  • The System Interfaces volume of POSIX.1‐2017, read(), readv(), write(), writev()

go read those next bestie, that's the reading list. 📚

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 page, bestie!! brought to you by IEEE/The Open Group, dated 2017, filed under sys_uio.h(7POSIX). tysm for reading, go forth and gather your I/O vectors responsibly 💖✨🎀

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