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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
       _toupper — transliterate lowercase characters to uppercase


SYNOPSIS
       #include <ctype.h>

       int _toupper(int c);


DESCRIPTION
       The  _toupper()  macro  shall be equivalent to toupper() except that the application shall
       ensure that the argument c is a lowercase letter.


RETURN VALUE
       Upon successful completion, _toupper() shall return the uppercase letter corresponding  to
       the argument passed.


ERRORS
       No errors are defined.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       Applications  should  use  the  toupper()  function  instead of the obsolescent _toupper()
       function.


RATIONALE
       None.


FUTURE DIRECTIONS
       The _toupper() function may be removed in a future version.


SEE ALSO
       islower(), toupper()

       The Base Definitions volume of POSIX.1‐2017, Chapter 7, Locale, <ctype.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 .