mirror of https://github.com/mkerrisk/man-pages
192 lines
4.6 KiB
Groff
192 lines
4.6 KiB
Groff
.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
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.\" and Copyright 2014 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" Modified Sat Jul 24 17:45:39 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified 2000-02-13 by Nicolás Lichtmaier <nick@debian.org>
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.TH TOUPPER 3 2016-10-08 "GNU" "Linux Programmer's Manual"
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.SH NAME
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toupper, tolower, toupper_l, tolower_l \- convert uppercase or lowercase
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.SH SYNOPSIS
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.nf
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.B #include <ctype.h>
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.sp
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.BI "int toupper(int " "c" );
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.br
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.BI "int tolower(int " "c" );
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.BI "int toupper_l(int " c ", locale_t " locale );
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.BI "int tolower_l(int " c ", locale_t " locale );
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR toupper_l (),
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.BR tolower_l ():
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.PD 0
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.RS 4
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.TP
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Since glibc 2.10:
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_XOPEN_SOURCE\ >=\ 700
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.TP
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Before glibc 2.10:
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_GNU_SOURCE
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.RE
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.PD
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.SH DESCRIPTION
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These functions convert lowercase letters to uppercase, and vice versa.
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If
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.I c
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is a lowercase letter,
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.BR toupper ()
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returns its uppercase equivalent,
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if an uppercase representation exists in the current locale.
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Otherwise, it returns
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.IR c .
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The
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.BR toupper_l ()
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function performs the same task,
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but uses the locale referred to by the locale handle
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.IR locale .
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If
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.I c
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is an uppercase letter,
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.BR tolower ()
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returns its lowercase equivalent,
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if a lowercase representation exists in the current locale.
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Otherwise, it returns
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.IR c .
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The
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.BR tolower_l ()
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function performs the same task,
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but uses the locale referred to by the locale handle
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.IR locale .
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.PP
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If
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.I c
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is neither an
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.I "unsigned char"
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value nor
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.BR EOF ,
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the behavior of these functions
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is undefined.
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The behavior of
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.BR toupper_l ()
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and
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.BR tolower_l ()
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is undefined if
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.I locale
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is the special locale object
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.BR LC_GLOBAL_LOCALE
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(see
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.BR duplocale (3))
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or is not a valid locale object handle.
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.SH RETURN VALUE
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The value returned is that of the converted letter, or
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.I c
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if the conversion was not possible.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw24 lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR toupper (),
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.BR tolower (),
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.br
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.BR toupper_l (),
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.BR tolower_l ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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.BR toupper (),
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.BR tolower ():
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C89, C99, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
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.BR toupper_l (),
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.BR tolower_l ():
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POSIX.1-2008.
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.SH NOTES
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The standards require that the argument
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.I c
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for these functions is either
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.B EOF
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or a value that is representable in the type
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.IR "unsigned char" .
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If the argument
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.I c
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is of type
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.IR char ,
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it must be cast to
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.IR "unsigned char" ,
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as in the following example:
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.nf
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.in +4n
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char c;
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\&...
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res = toupper((unsigned char) c);
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.in
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.fi
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This is necessary because
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.I char
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may be the equivalent
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.IR "signed char" ,
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in which case a byte where the top bit is set would be sign extended when
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converting to
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.IR int ,
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yielding a value that is outside the range of
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.IR "unsigned char" .
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The details of what constitutes an uppercase or lowercase letter depend
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on the locale.
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For example, the default
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.B """C"""
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locale does not know about umlauts, so no conversion is done for them.
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.PP
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In some non-English locales, there are lowercase letters with no
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corresponding uppercase equivalent;
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.\" FIXME One day the statement about "sharp s" needs to be reworked,
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.\" since there is nowadays a capital "sharp s" that has a codepoint
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.\" in Unicode 5.0; see https://en.wikipedia.org/wiki/Capital_%E1%BA%9E
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the German sharp s is one example.
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.SH SEE ALSO
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.BR isalpha (3),
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.BR newlocale (3),
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.BR setlocale (3),
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.BR towlower (3),
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.BR towupper (3),
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.BR uselocale (3),
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.BR locale (7)
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