VFWPRINTF(3POSIX)

💖 VFWPRINTF(3POSIX) 💖

okay bestie, welcome to the POSIX Programmer's Manual — this page is literally called VFWPRINTF(3POSIX) and it's the whole wide-character stdarg situation, and I'm so excited to explain it to you 🎀

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✨ PROLOG ✨

so like, this manual page is part of the POSIX Programmer's Manual. that's the vibe.

⚠️ the Linux implementation of this interface may differ (bestie, please consult the corresponding Linux manual page for details on Linux behavior), or honestly the interface may not be implemented on Linux at all. not me being vague but accurate 💀

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🌸 NAME 🌸

vfwprintf, vswprintf, vwprintf — wide-character formatted output of a stdarg argument list. it's giving "printf but wide and also it takes a va_list" 💅

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🦋 SYNOPSIS 🦋

#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>

int vfwprintf(FILE *restrict stream, const wchar_t *restrict format,
    va_list arg);
int vswprintf(wchar_t *restrict ws, size_t n,
    const wchar_t *restrict format, va_list arg);
int vwprintf(const wchar_t *restrict format, va_list arg);

three icons, one header block, zero notes ✨

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👑 DESCRIPTION 👑

the functionality described on this reference page is aligned with the ISO C standard. if there's any conflict between what's required here and the ISO C standard, that's unintentional, fr fr. this volume of POSIX.1‐2017 defers to the ISO C standard. periodt.

so vfwprintf(), vswprintf(), and vwprintf() are the equivalent of fwprintf(), swprintf(), and wprintf() respectively — same energy, same vibes — except that instead of getting called with a variable number of arguments, they get called with an argument list as defined by <stdarg.h>. that's the whole plot twist.

these functions shall not invoke the va_end macro. okay but here's the tea 😭 — as these functions do invoke the va_arg macro, the value of ap after the return is unspecified. so like... don't be surprised. it's giving undefined-ish energy and we respect it.

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🍓 RETURN VALUE 🍓

refer to fwprintf(). that's it, that's the whole section, i'm not going to elaborate because the manpage didn't 💅

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🌈 ERRORS 🌈

refer to fwprintf(). again. short king behavior.

and then it says: the following sections are informative. so everything from here on out is informative, bestie, not normative 🫶

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🎀 EXAMPLES 🎀

None.

literally nothing. empty. the silence is deafening 💀

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🧚 APPLICATION USAGE 🧚

apps using these functions should call va_end(ap) afterwards to clean up. that's the self-care part. do it. don't skip it. your va_list deserves closure ✨

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💜 RATIONALE 💜

None.

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⭐ FUTURE DIRECTIONS ⭐

None.

the future is... nothing? iconic honestly 👑

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🔥 SEE ALSO 🔥

• Section 2.5, Standard I/O Streams, fwprintf()
• The Base Definitions volume of POSIX.1‐2017, <stdarg.h>, <stdio.h>, <wchar.h>

go read those if you want the full lore iykyk 📚

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💅 COPYRIGHT 💅

okay legal bestie moment, gotta keep this exact because it's the law:

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 .

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and that's the whole page, bestie 🦋 this was IEEE/The Open Group, 2017, VFWPRINTF(3POSIX) — thanks for reading my little manpage rant, mwah 💖