WCSRTOMBS(3P)

🦋 PROLOG 🦋

Okay bestie, real talk before we get into it — this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so pls go consult the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface might just not be implemented on Linux at all. Not me warning you upfront 💀

---

✨ NAME ✨

wcsnrtombs, wcsrtombs — convert a wide-character string to a character string (restartable)

So this is the WCSRTOMBS(3P) page, from the POSIX Programmer's Manual, and it's giving wide-char-to-narrow-char glow-up energy ✨

---

🌸 SYNOPSIS 🌸

#include <wchar.h>

size_t wcsnrtombs(char *restrict dst, const wchar_t **restrict src,
    size_t nwc, size_t len, mbstate_t *restrict ps);
size_t wcsrtombs(char *restrict dst, const wchar_t **restrict src,
    size_t len, mbstate_t *restrict ps);

---

💖 DESCRIPTION 💖

For wcsrtombs(): heads up, the functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard. (Iconic of POSIX honestly, it knows who the main character is 👑)

The wcsrtombs() function shall convert a sequence of wide characters from the array indirectly pointed to by src into a sequence of corresponding characters, beginning in the conversion state described by the object pointed to by ps. If dst is not a null pointer, the converted characters shall then be stored into the array pointed to by dst. Conversion continues up to and including a terminating null wide character, which shall also be stored. Conversion shall stop earlier in the following cases:

• When a code is reached that does not correspond to a valid character
• When the next character would exceed the limit of len total bytes to be stored in the array pointed to by dst (and dst is not a null pointer)

Each conversion shall take place as if by a call to the wcrtomb() function. No cap. 🫶

If dst is not a null pointer, the pointer object pointed to by src shall be assigned either a null pointer (if conversion stopped due to reaching a terminating null wide character) or the address just past the last wide character converted (if any). If conversion stopped due to reaching a terminating null wide character, the resulting state described shall be the initial conversion state.

If ps is a null pointer, the wcsrtombs() function shall use its own internal mbstate_t object, which is initialized at program start-up to the initial conversion state. Otherwise, the mbstate_t object pointed to by ps shall be used to completely describe the current conversion state of the associated character sequence.

⚠️ Note bestie: the wcsnrtombs() and wcsrtombs() functions need not be thread-safe if called with a NULL ps argument. So like... be mindful, okay? 🙈

The wcsnrtombs() function shall be equivalent to the wcsrtombs() function, except that the conversion is limited to the first nwc wide characters. That's literally the whole diff, she's just a version of her sister with a cap on how many wide chars she'll look at 💅

The wcsrtombs() function shall not change the setting of errno if successful. (Polite behavior, we love to see it ✨)

The behavior of these functions shall be affected by the LC_CTYPE category of the current locale. Locale girlies, this one's for you 🌈

The implementation shall behave as if no function defined in System Interfaces volume of POSIX.1‐2017 calls these functions.

---

🔥 RETURN VALUE 🔥

If conversion stops because a code is reached that does not correspond to a valid character, an encoding error occurs. In this case, these functions shall store the value of the macro [EILSEQ] in errno and return (size_t)-1; the conversion state is undefined. 😭 (Yes undefined. Not "probably fine". Undefined undefined. Do not touch.)

Otherwise, these functions shall return the number of bytes in the resulting character sequence, not including the terminating null (if any).

---

💜 ERRORS 💜

These functions shall fail if:

• EILSEQ — A wide-character code does not correspond to a valid character.

These functions may fail if:

• EINVAL — ps points to an object that contains an invalid conversion state.

The following sections are informative.

---

🎀 EXAMPLES 🎀

None.

(I know. Nothing. The audacity.)

---

🧚 APPLICATION USAGE 🧚

None.

---

💜 RATIONALE 💜

None.

---

⭐ FUTURE DIRECTIONS ⭐

None.

---

🌈 SEE ALSO 🌈

• mbsinit(), wcrtomb()
• The Base Definitions volume of POSIX.1‐2017, <wchar.h>

---

👑 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. 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, we ate and left no crumbs 💅✨

this was brought to you by IEEE/The Open Group, 2017 — the 2017 girlies really said "here's your man page, now go read the ISO C standard" 🫶 see u next time, mwah 💖