1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
'\" t
.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
.\" and Copyright 2014 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" Modified Sat Jul 24 17:45:39 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2000-02-13 by Nicolás Lichtmaier <nick@debian.org>
.TH toupper 3 2024-02-25 "Linux man-pages 6.7"
.SH NAME
toupper, tolower, toupper_l, tolower_l \- convert uppercase or lowercase
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <ctype.h>
.P
.BI "int toupper(int " "c" );
.BI "int tolower(int " "c" );
.P
.BI "int toupper_l(int " c ", locale_t " locale );
.BI "int tolower_l(int " c ", locale_t " locale );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.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.
.P
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 .
.P
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 .
.P
If
.I c
is neither an
.I "unsigned char"
value nor
.BR EOF ,
the behavior of these functions
is undefined.
.P
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).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR toupper (),
.BR tolower (),
.BR toupper_l (),
.BR tolower_l ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
.TP
.BR toupper ()
.TQ
.BR tolower ()
C11, POSIX.1-2008.
.TP
.BR toupper_l ()
.TQ
.BR tolower_l ()
POSIX.1-2008.
.SH HISTORY
.TP
.BR toupper ()
.TQ
.BR tolower ()
C89, 4.3BSD, POSIX.1-2001.
.TP
.BR toupper_l ()
.TQ
.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:
.P
.in +4n
.EX
char c;
\&...
res = toupper((unsigned char) c);
.EE
.in
.P
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" .
.P
The details of what constitutes an uppercase or lowercase letter depend
on the locale.
For example, the default
.B \[dq]C\[dq]
locale does not know about umlauts, so no conversion is done for them.
.P
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)
|
