---
name: "wcsxfrm"
section: "3p"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/wcsxfrm/3p"
---

# wcsxfrm(3p)

wide-character string transformation

## PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

## NAME

wcsxfrm, wcsxfrm\_l — wide-character string transformation

## SYNOPSIS

```
#include <wchar.h>
```

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

## DESCRIPTION

For *wcsxfrm*(): 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.

The *wcsxfrm*() and *wcsxfrm\_l*() functions shall transform the wide-character string pointed to by *ws2* and place the resulting wide-character string into the array pointed to by *ws1*. The transformation shall be such that if *wcscmp*() is applied to two transformed wide strings, it shall return a value greater than, equal to, or less than 0, corresponding to the result of *wcscoll*() and *wcscoll\_l*() applied to the same two original wide-character strings, and the same *LC\_COLLATE* category of the current locale or the locale object *locale*, respectively. No more than *n* wide-character codes shall be placed into the resulting array pointed to by *ws1*, including the terminating null wide-character code. If *n* is 0, *ws1* is permitted to be a null pointer. If copying takes place between objects that overlap, the behavior is undefined.

The *wcsxfrm*() and *wcsxfrm\_l*() functions shall not change the setting of *errno* if successful.

Since no return value is reserved to indicate an error, an application wishing to check for error situations should set *errno* to 0, then call *wcsxfrm*() or *wcsxfrm\_l*(), then check *errno*.

The behavior is undefined if the *locale* argument to *wcsxfrm\_l*() is the special locale object LC\_GLOBAL\_LOCALE or is not a valid locale object handle.

## RETURN VALUE

The *wcsxfrm*() and *wcsxfrm\_l*() functions shall return the length of the transformed wide-character string (not including the terminating null wide-character code). If the value returned is *n* or more, the contents of the array pointed to by *ws1* are unspecified.

On error, the *wcsxfrm*() and *wcsxfrm\_l*() functions may set *errno*, but no return value is reserved to indicate an error.

## ERRORS

These functions may fail if:

- **EINVAL**

  The wide-character string pointed to by *ws2* contains wide-character codes outside the domain of the collating sequence.

*The following sections are informative.*

## EXAMPLES

None.

## APPLICATION USAGE

The transformation function is such that two transformed wide-character strings can be ordered by *wcscmp*() as appropriate to collating sequence information in the current locale (category *LC\_COLLATE*).

The fact that when *n* is 0 *ws1* is permitted to be a null pointer is useful to determine the size of the *ws1* array prior to making the transformation.

## RATIONALE

None.

## FUTURE DIRECTIONS

None.

## SEE ALSO

*wcscmp()*, *wcscoll()*

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 .