This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       The  transformation  function  is  such  that  two  transformed  strings  can  be  ordered by strcmp() as
       appropriate to collating sequence information in the current locale (category LC_COLLATE).

       The fact that when n is 0 s1 is permitted to be a null pointer is useful to determine the size of the  s1
       array prior to making the transformation.

       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 .

IEEE/The Open Group                                   2017                                       STRXFRM(3POSIX)

       For strxfrm(): 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 strxfrm() and strxfrm_l() functions shall transform the  string  pointed  to  by  s2  and  place  the
       resulting string into the array pointed to by s1.  The transformation is such that if strcmp() is applied
       to two transformed strings, it shall return a value greater than, equal to, or less than 0, corresponding
       to  the  result  of strcoll() or strcoll_l(), respectively, applied to the same two original strings with
       the same locale.  No more than n bytes are placed into the resulting array pointed to  by  s1,  including
       the  terminating  NUL  character. If n is 0, s1 is permitted to be a null pointer. If copying takes place
       between objects that overlap, the behavior is undefined.

       The strxfrm() and strxfrm_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 strxfrm() or strxfrm_l(), then check errno.

       The  behavior  is  undefined  if  the  locale  argument  to  strxfrm_l()  is  the  special  locale object
       LC_GLOBAL_LOCALE or is not a valid locale object handle.

       These functions may fail if:

       EINVAL The string pointed to by the s2 argument contains characters outside the domain of  the  collating
              sequence.

       Thefollowingsectionsareinformative.

       None.

       None.

       strxfrm, strxfrm_l — string transformation

       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.

       None.

       Upon successful completion, strxfrm() and strxfrm_l() shall return the length of the  transformed  string
       (not  including  the  terminating NUL character). If the value returned is n or more, the contents of the
       array pointed to by s1 are unspecified.

       On error, strxfrm() and strxfrm_l() may set errno but no return value is reserved to indicate an error.

strcmp(), strcoll()

       The Base Definitions volume of POSIX.1‐2017, <string.h>

       #include <string.h>

       size_t strxfrm(char *restrict s1, const char *restrict s2, size_t n);
       size_t strxfrm_l(char *restrict s1, const char *restrict s2,
           size_t n, locale_t locale);