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

       tolower, tolower_l — transliterate uppercase characters to lowercase

SYNOPSIS

       #include <ctype.h>

       int tolower(int c);
       int tolower_l(int c, locale_t locale);

DESCRIPTION

       For  tolower():  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 tolower() and tolower_l() functions have as a domain a type int, the value of which is
       representable as an unsigned char or the value of EOF.  If  the  argument  has  any  other
       value,  the  behavior is undefined. If the argument of tolower() or tolower_l() represents
       an uppercase letter, and there exists a  corresponding  lowercase  letter  as  defined  by
       character  type  information in the current locale or in the locale represented by locale,
       respectively (category LC_CTYPE), the result shall be the corresponding lowercase  letter.
       All other arguments in the domain are returned unchanged.

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

RETURN VALUE

       Upon successful completion, the tolower()  and  tolower_l()  functions  shall  return  the
       lowercase  letter  corresponding  to the argument passed; otherwise, they shall return the
       argument unchanged.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       setlocale(), uselocale()

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