VFPRINTF(3P)

💖 VFPRINTF(3P) — POSIX Programmer's Manual 💖

okay bestie, this one's from the POSIX Programmer's Manual, so let's get into it 💅

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✨ PROLOG ✨

so like, this manual page is part of the POSIX Programmer's Manual, right? but heads up — the Linux implementation of this interface may differ, so if you're on Linux pls consult the corresponding Linux manual page for the deets on Linux behavior 🫶. also possible: the interface just isn't implemented on Linux at all. tragic, but true. 💀

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🎀 NAME 🎀

vdprintf, vfprintf, vprintf, vsnprintf, vsprintf — format output of a stdarg argument list ✨

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🦋 SYNOPSIS 🦋

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

int vdprintf(int fildes, const char *restrict format, va_list ap);
int vfprintf(FILE *restrict stream, const char *restrict format,
    va_list ap);
int vprintf(const char *restrict format, va_list ap);
int vsnprintf(char *restrict s, size_t n, const char *restrict format,
    va_list ap);
int vsprintf(char *restrict s, const char *restrict format, va_list ap);

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🌸 DESCRIPTION 🌸

okay so the functionality described on this reference page is aligned with the ISO C standard. if there's any conflict between the requirements described here and the ISO C standard, that conflict is unintentional — no cap. this volume of POSIX.1‐2017 defers to the ISO C standard, periodt. 👑

so the way that vdprintf(), vfprintf(), vprintf(), vsnprintf(), and vsprintf() work is: they shall be equivalent to the dprintf(), fprintf(), printf(), snprintf(), and sprintf() functions respectively — like, same energy, same output — except that instead of being called with a variable number of arguments, they're called with an argument list as defined by <stdarg.h>. that's literally the whole twist. 🧚

⚠️ also these functions shall not invoke the va_end macro. and since these functions invoke the va_arg macro, the value of ap after the return is unspecified. so don't come for ap after, it's giving mystery. 💀

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💜 RETURN VALUE 💜

refer to fprintf(). that's it, that's the section. 💅

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⭐ ERRORS ⭐

refer to fprintf(). 👑

the following sections are informative (iykyk — that means they're not normative, bestie).

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🌈 EXAMPLES 🌈

None. 😭 iconic of them honestly.

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🍓 APPLICATION USAGE 🍓

apps using these functions should call va_end(ap) afterwards to clean up. do it. be a clean, responsible main character. 🫶

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🔥 RATIONALE 🔥

None. 💀

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🎀 FUTURE DIRECTIONS 🎀

None. ✨

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👑 SEE ALSO 👑

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

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💖 COPYRIGHT 💖

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. so like, if they disagree, the original wins, no debate. 🫶

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 vibe check bestie 💅 this page came to you courtesy of IEEE/The Open Group, 2017, under the manual name VFPRINTF(3P) — slay, you're now fully fluent, go forth and format ur output 🌟🦋✨