| .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) |
| .\" and Copyright 2014 Michael Kerrisk <mtk.manpages@gmail.com> |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
| .\" manual provided the copyright notice and this permission notice are |
| .\" preserved on all copies. |
| .\" |
| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
| .\" the use of the information contained herein. The author(s) may not |
| .\" have taken the same level of care in the production of this manual, |
| .\" which is licensed free of charge, as they might when working |
| .\" professionally. |
| .\" |
| .\" Formatted or processed versions of this manual, if unaccompanied by |
| .\" the source, must acknowledge the copyright and authors of this work. |
| .\" %%%LICENSE_END |
| .\" |
| .\" Modified Sat Jul 24 17:45:39 1993 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified 2000-02-13 by Nicolรกs Lichtmaier <nick@debian.org> |
| .TH TOUPPER 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| toupper, tolower, toupper_l, tolower_l \- convert uppercase or lowercase |
| .SH SYNOPSIS |
| .nf |
| .B #include <ctype.h> |
| .PP |
| .BI "int toupper(int " "c" ); |
| .BI "int tolower(int " "c" ); |
| .PP |
| .BI "int toupper_l(int " c ", locale_t " locale ); |
| .BI "int tolower_l(int " c ", locale_t " locale ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR toupper_l (), |
| .BR tolower_l (): |
| .nf |
| Since glibc 2.10: |
| _XOPEN_SOURCE >= 700 |
| Before glibc 2.10: |
| _GNU_SOURCE |
| .fi |
| .SH DESCRIPTION |
| These functions convert lowercase letters to uppercase, and vice versa. |
| .PP |
| If |
| .I c |
| is a lowercase letter, |
| .BR toupper () |
| returns its uppercase equivalent, |
| if an uppercase representation exists in the current locale. |
| Otherwise, it returns |
| .IR c . |
| The |
| .BR toupper_l () |
| function performs the same task, |
| but uses the locale referred to by the locale handle |
| .IR locale . |
| .PP |
| If |
| .I c |
| is an uppercase letter, |
| .BR tolower () |
| returns its lowercase equivalent, |
| if a lowercase representation exists in the current locale. |
| Otherwise, it returns |
| .IR c . |
| The |
| .BR tolower_l () |
| function performs the same task, |
| but uses the locale referred to by the locale handle |
| .IR locale . |
| .PP |
| If |
| .I c |
| is neither an |
| .I "unsigned char" |
| value nor |
| .BR EOF , |
| the behavior of these functions |
| is undefined. |
| .PP |
| The behavior of |
| .BR toupper_l () |
| and |
| .BR tolower_l () |
| is undefined if |
| .I locale |
| is the special locale object |
| .B LC_GLOBAL_LOCALE |
| (see |
| .BR duplocale (3)) |
| or is not a valid locale object handle. |
| .SH RETURN VALUE |
| The value returned is that of the converted letter, or |
| .I c |
| if the conversion was not possible. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR toupper (), |
| .BR tolower (), |
| .BR toupper_l (), |
| .BR tolower_l () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| .BR toupper (), |
| .BR tolower (): |
| C89, C99, 4.3BSD, POSIX.1-2001, POSIX.1-2008. |
| .PP |
| .BR toupper_l (), |
| .BR tolower_l (): |
| POSIX.1-2008. |
| .SH NOTES |
| The standards require that the argument |
| .I c |
| for these functions is either |
| .B EOF |
| or a value that is representable in the type |
| .IR "unsigned char" . |
| If the argument |
| .I c |
| is of type |
| .IR char , |
| it must be cast to |
| .IR "unsigned char" , |
| as in the following example: |
| .PP |
| .in +4n |
| .EX |
| char c; |
| \&... |
| res = toupper((unsigned char) c); |
| .EE |
| .in |
| .PP |
| This is necessary because |
| .I char |
| may be the equivalent |
| .IR "signed char" , |
| in which case a byte where the top bit is set would be sign extended when |
| converting to |
| .IR int , |
| yielding a value that is outside the range of |
| .IR "unsigned char" . |
| .PP |
| The details of what constitutes an uppercase or lowercase letter depend |
| on the locale. |
| For example, the default |
| .B """C""" |
| locale does not know about umlauts, so no conversion is done for them. |
| .PP |
| In some non-English locales, there are lowercase letters with no |
| corresponding uppercase equivalent; |
| .\" FIXME One day the statement about "sharp s" needs to be reworked, |
| .\" since there is nowadays a capital "sharp s" that has a codepoint |
| .\" in Unicode 5.0; see https://en.wikipedia.org/wiki/Capital_%E1%BA%9E |
| the German sharp s is one example. |
| .SH SEE ALSO |
| .BR isalpha (3), |
| .BR newlocale (3), |
| .BR setlocale (3), |
| .BR towlower (3), |
| .BR towupper (3), |
| .BR uselocale (3), |
| .BR locale (7) |