_TOLOWER(3POSIX) POSIX Programmer's Manual _TOLOWER(3POSIX)
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.
_tolower — transliterate uppercase characters to lowercase
int _tolower(int c);
The _tolower() macro shall be equivalent to tolower(c) except that the application shall
ensure that the argument c is an uppercase letter.
Upon successful completion, _tolower() shall return the lowercase letter corresponding to
the argument passed.
No errors are defined.
The following sections are informative.
Applications should use the tolower() function instead of the obsolescent _tolower() func‐
The _tolower() function may be removed in a future version.
The Base Definitions volume of POSIX.1‐2008, Chapter 7, Locale, <ctype.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrep‐
ancy 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.unix.org/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 2013 _TOLOWER(3POSIX)