The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
A newer edition of this document exists here


wcsxfrm - wide-character string transformation


#include <wchar.h>

size_t wcsxfrm(wchar_t *restrict
ws1, const wchar_t *restrict ws2,


[CX] [Option Start] 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 IEEE Std 1003.1-2001 defers to the ISO C standard. [Option End]

The wcsxfrm() function 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() applied to the same two original wide-character strings. 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.

[CX] [Option Start] The wcsxfrm() function 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(), then check errno. [Option End]


The wcsxfrm() function 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.

[CX] [Option Start] On error, the wcsxfrm() function may set errno, but no return value is reserved to indicate an error. [Option End]


The wcsxfrm() function may fail if:

[CX] [Option Start] The wide-character string pointed to by ws2 contains wide-character codes outside the domain of the collating sequence. [Option End]

The following sections are informative.




The transformation function is such that two transformed wide-character strings can be ordered by wcscmp() as appropriate to collating sequence information in the program's 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.






wcscmp(), wcscoll(), the Base Definitions volume of IEEE Std 1003.1-2001, <wchar.h>


First released in Issue 4. Derived from the MSE working draft.

Issue 5

Moved from ENHANCED I18N to BASE and the [ENOSYS] error is removed.

The DESCRIPTION is updated to indicate that errno is not changed if the function is successful.

Issue 6

In previous versions, this function was required to return -1 on error.

Extensions beyond the ISO C standard are marked.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

The wcsxfrm() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.

End of informative text.

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