WCSTOUL(3P)

💖 WCSTOUL(3P) 💖 the wide-char glow-up

okay so before anything else: this page is part of the POSIX Programmer's Manual. bestie listen — the Linux implementation of this interface may differ (so like, go consult the corresponding Linux manual page for the actual Linux behavior), or honestly? the interface may not be implemented on Linux at all. 🙈 no cap.

---

✨ NAME ✨

wcstoul, wcstoull — convert a wide-character string to an unsigned long

---

🎀 SYNOPSIS 🎀

#include <wchar.h>

unsigned long wcstoul(const wchar_t *restrict nptr,
    wchar_t **restrict endptr, int base);
unsigned long long wcstoull(const wchar_t *restrict nptr,
    wchar_t **restrict endptr, int base);

---

🦋 DESCRIPTION 🦋

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. (posix said "iso c is the referee, i don't wanna fight" 💅)

So the wcstoul() and wcstoull() functions shall convert the initial portion of the wide-character string pointed to by nptr to unsigned long and unsigned long long representation, respectively. First, they shall decompose the input wide-character string into three parts:

1. An initial, possibly empty, sequence of white-space wide-character codes (as specified by iswspace())
2. A subject sequence interpreted as an integer represented in some radix determined by the value of base
3. A final wide-character string of one or more unrecognized wide-character codes, including the terminating null wide-character code of the input wide-character string

Then they shall attempt to convert the subject sequence to an unsigned integer, and return the result. periodt.

If base is 0, the expected form of the subject sequence is that of a decimal constant, octal constant, or hexadecimal constant, any of which may be preceded by a '+' or '-' sign. A decimal constant begins with a non-zero digit, and consists of a sequence of decimal digits. An octal constant consists of the prefix '0' optionally followed by a sequence of the digits '0' to '7' only. A hexadecimal constant consists of the prefix 0x or 0X followed by a sequence of the decimal digits and letters 'a' (or 'A') to 'f' (or 'F') with values 10 to 15 respectively.

If the value of base is between 2 and 36, the expected form of the subject sequence is a sequence of letters and digits representing an integer with the radix specified by base, optionally preceded by a '+' or '-' sign, but not including an integer suffix. The letters from 'a' (or 'A') to 'z' (or 'Z') inclusive are ascribed the values 10 to 35; only letters whose ascribed values are less than that of base shall be permitted. If the value of base is 16, the wide-character codes 0x or 0X may optionally precede the sequence of letters and digits, following the sign if present.

The subject sequence is defined as the longest initial subsequence of the input wide-character string, starting with the first wide-character code that is not white space and is of the expected form. The subject sequence contains no wide-character codes if the input wide-character string is empty or consists entirely of white-space wide-character codes, or if the first wide-character code that is not white space is other than a sign or a permissible letter or digit. (basically: nothing to grab onto → nothing gets grabbed 🫶)

If the subject sequence has the expected form and base is 0, the sequence of wide-character codes starting with the first digit shall be interpreted as an integer constant. If the subject sequence has the expected form and the value of base is between 2 and 36, it shall be used as the base for conversion, ascribing to each letter its value as given above. If the subject sequence begins with a <hyphen-minus>, the value resulting from the conversion shall be negated. A pointer to the final wide-character string shall be stored in the object pointed to by endptr, provided that endptr is not a null pointer.

In other than the C or POSIX locale, additional locale-specific subject sequence forms may be accepted. 🌍

If the subject sequence is empty or does not have the expected form, no conversion shall be performed; the value of nptr shall be stored in the object pointed to by endptr, provided that endptr is not a null pointer.

These functions shall not change the setting of errno if successful.

⚠️ okay so this is the part everyone fumbles: since 0, {ULONG_MAX}, and {ULLONG_MAX} are returned on error and 0 is also a valid return on success, an application wishing to check for error situations should set errno to 0, then call wcstoul() or wcstoull(), then check errno. that's the whole ritual. do not skip the ritual. 😭

---

👑 RETURN VALUE 👑

Upon successful completion, the wcstoul() and wcstoull() functions shall return the converted value, if any. If no conversion could be performed, 0 shall be returned and errno may be set to indicate the error. If the correct value is outside the range of representable values, {ULONG_MAX} or {ULLONG_MAX} respectively shall be returned and errno set to [ERANGE]. it's giving "i tried my best and hit the ceiling" 💀

---

🔥 ERRORS 🔥

These functions shall fail if:

• EINVAL — The value of base is not supported.
• ERANGE — The value to be returned is not representable.

These functions may fail if:

• EINVAL — No conversion could be performed.

The following sections are informative.

---

🍓 EXAMPLES 🍓

None.

---

🌈 APPLICATION USAGE 🌈

None.

---

🧚 RATIONALE 🧚

None.

---

⭐ FUTURE DIRECTIONS ⭐

None.

---

💜 SEE ALSO 💜

fscanf(), iswalpha(), wcstod(), wcstol()

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 .

---

okay that's the whole thing, you absolutely ate this one bestie 💅✨ this page came to you courtesy of IEEE/The Open Group, dated 2017 — and wcstoul(3P) is sending you off with a lil kiss. 🫶💖