xref: /netbsd/lib/libc/gen/ctype.3 (revision 6550d01e)
1.\"	$NetBSD: ctype.3,v 1.21 2010/05/06 11:46:11 jruoho Exp $
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31.\"     @(#)ctype.3	6.5 (Berkeley) 4/19/91
32.\"
33.Dd May 6, 2010
34.Dt CTYPE 3
35.Os
36.Sh NAME
37.Nm isalpha ,
38.Nm isupper ,
39.Nm islower ,
40.Nm isdigit ,
41.Nm isxdigit ,
42.Nm isalnum ,
43.Nm isspace ,
44.Nm ispunct ,
45.Nm isprint ,
46.Nm isgraph ,
47.Nm iscntrl ,
48.Nm isblank ,
49.Nm toupper ,
50.Nm tolower ,
51.Nd character classification and mapping functions
52.Sh LIBRARY
53.Lb libc
54.Sh SYNOPSIS
55.In ctype.h
56.Fn isalpha "int c"
57.Fn isupper "int c"
58.Fn islower "int c"
59.Fn isdigit "int c"
60.Fn isxdigit "int c"
61.Fn isalnum "int c"
62.Fn isspace "int c"
63.Fn ispunct "int c"
64.Fn isprint "int c"
65.Fn isgraph "int c"
66.Fn iscntrl "int c"
67.Fn isblank "int c"
68.Fn toupper "int c"
69.Fn tolower "int c"
70.Sh DESCRIPTION
71The above functions perform character tests and conversions on the integer
72.Ar c .
73.Pp
74See the specific manual pages for information about the
75test or conversion performed by each function.
76.Sh EXAMPLES
77To print an upper-case version of a string to stdout,
78the following code can be used:
79.Bd -literal -offset indent
80const char *s = "xyz";
81
82while (*s != '\e0') {
83    putchar(toupper((int)(unsigned char)*s));
84    s++;
85}
86.Ed
87.Sh SEE ALSO
88.Xr isalnum 3 ,
89.Xr isalpha 3 ,
90.Xr isblank 3 ,
91.Xr iscntrl 3 ,
92.Xr isdigit 3 ,
93.Xr isgraph 3 ,
94.Xr islower 3 ,
95.Xr isprint 3 ,
96.Xr ispunct 3 ,
97.Xr isspace 3 ,
98.Xr isupper 3 ,
99.Xr isxdigit 3 ,
100.Xr tolower 3 ,
101.Xr toupper 3 ,
102.Xr ascii 7
103.Sh STANDARDS
104These functions, with the exception of
105.Fn isblank ,
106conform to
107.St -ansiC .
108All described functions, including
109.Fn isblank ,
110also conform to
111.St -p1003.1-2001 .
112.Sh CAVEATS
113The first argument of these functions is of type
114.Vt int ,
115but only a very restricted subset of values are actually valid.
116The argument must either be the value of the macro
117.Dv EOF
118(which has a negative value),
119or must be a non-negative value within the range representable as
120.Vt unsigned char .
121Passing invalid values leads to undefined behavior.
122.Pp
123Values of type
124.Vt int
125that were returned by
126.Xr getc 3 ,
127.Xr fgetc 3 ,
128and similar functions or macros
129are already in the correct range, and may be safely passed to these
130.Nm ctype
131functions without any casts.
132.Pp
133Values of type
134.Vt char
135or
136.Vt signed char
137must first be cast to
138.Vt unsigned char ,
139to ensure that the values are within the correct range.
140The result should then be cast to
141.Vt int
142to avoid warnings from some compilers.
143Casting a negative-valued
144.Vt char
145or
146.Vt signed char
147directly to
148.Vt int
149will produce a negative-valued
150.Vt int ,
151which will be outside the range of allowed values
152(unless it happens to be equal to
153.Dv EOF ,
154but even that would not give the desired result).
155