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

       The strings "tolower" and "toupper" are reserved for the standard mapping names. In the table below,  the
       functions in the left column are equivalent to the functions in the right column.

           towlower(wc)            towctrans(wc, wctrans("tolower"))
           towlower_l(wc, locale)  towctrans_l(wc, wctrans("tolower"), locale)
           towupper(wc)            towctrans(wc, wctrans("toupper"))
           towupper_l(wc, locale)  towctrans_l(wc, wctrans("toupper"), locale)

       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                                     TOWCTRANS(3POSIX)

       For  towctrans():  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 towctrans() and towctrans_l() functions shall transliterate the  wide-character  code  wc  using  the
       mapping described by desc.

       The  current  setting  of  the  LC_CTYPE  category  in the current locale or in the locale represented by
       locale, respectively, should be the same as during the call to wctrans() or wctrans_l() that returned the
       value desc.

       If the value of desc is invalid (that is, not obtained by a call to wctrans() or desc is invalidated by a
       subsequent call to setlocale() that has affected category LC_CTYPE), the result is unspecified.

       If the value of desc is invalid (that is, not obtained by a call to  wctrans_l()  with  the  same  locale
       object locale) the result is unspecified.

       An  application wishing to check for error situations should set errno to 0 before calling towctrans() or
       towctrans_l().

       If errno is non-zero on return, an error has occurred.

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

       These functions may fail if:

       EINVALdesc contains an invalid transliteration descriptor.

       Thefollowingsectionsareinformative.

       None.

       None.

       towctrans, towctrans_l — wide-character transliteration

       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.

       If  successful, the towctrans() and towctrans_l() functions shall return the mapped value of wc using the
       mapping described by desc.  Otherwise, they shall return wc unchanged.

towlower(), towupper(), wctrans()

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

       #include <wctype.h>

       wint_t towctrans(wint_t wc, wctrans_t desc);
       wint_t towctrans_l(wint_t wc, wctrans_t desc,
           locale_t locale);