---
name: "wcsxfrm"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["freebsd", "macos"]
url: "https://new.carta.tech/wcsxfrm"
---

# wcsxfrm(3)

transform a wide string under locale

## NAME

**wcsxfrm**, **wcsxfrm\_l** – transform a wide string under locale

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<wchar.h\>**

*size\_t*\

**wcsxfrm**(*wchar\_t \*restrict ws1*, *const wchar\_t \*restrict ws2*, *size\_t n*);

**#include \<wchar.h\>**

**#include \<xlocale.h\>**

*size\_t*\

**wcsxfrm\_l**(*wchar\_t \*restrict ws1*, *const wchar\_t \*restrict ws2*, *size\_t n*, *locale\_t loc*);

## DESCRIPTION

The **wcsxfrm**() function transforms a null-terminated wide character string pointed to by *ws2*, according to the current locale's collation order, then copies the transformed string into *ws1*. No more than *n* wide characters are copied into *ws1*, including the terminating null character. If *n* is set to 0 (it helps to determine an actual size needed for transformation), *ws1* is permitted to be a NULL pointer.

Comparing two strings using **wcscmp**() after **wcsxfrm**() is equivalent to comparing two original strings with **wcscoll**().

Although the **wcsxfrm**() function uses the current locale, the **wcsxfrm\_l**() function may be passed a locale directly. See [xlocale(3)](/xlocale/3.md) for more information.

## RETURN VALUES

Upon successful completion, **wcsxfrm**() returns the length of the transformed string not including the terminating null character. If this value is *n* or more, the contents of *ws1* are indeterminate.

## SEE ALSO

[setlocale(3)](/setlocale/3.md), [strxfrm(3)](/strxfrm/3.md), [wcscmp(3)](/wcscmp/3.md), [wcscoll(3)](/wcscoll/3.md), [xlocale(3)](/xlocale/3.md)

## STANDARDS

The **wcsxfrm**() function conforms to ISO/IEC 9899:1999 (“ISO C99”).

## BUGS

The current implementation of **wcsxfrm**() only works in single-byte LC\_CTYPE locales, and falls back to using **wcsncpy**() in locales with extended character sets.

Comparing two strings using **wcscmp**() after **wcsxfrm**() is *not* always equivalent to comparison with **wcscoll**(); **wcsxfrm**() only stores information about primary collation weights into *ws1*, whereas **wcscoll**() compares characters using both primary and secondary weights.