1ctype(3C) Standard C Library Functions ctype(3C)
2
6 ctype, isalpha, isalnum, isascii, isblank, iscntrl, isdigit, islower,
7 isprint, isspace, isupper, ispunct, isgraph, isxdigit - character han‐
8 dling
9
11 #include <ctype.h>
12 int isalpha(int c);
14 int isalnum(int c);
17 int isascii(int c);
20 int isblank(int c);
23 int iscntrl(int c);
26 int isdigit(int c);
29 int isgraph(int c);
32 int islower(int c);
35 int isprint(int c);
38 int ispunct(int c);
41 int isspace(int c);
44 int isupper(int c);
47 int isxdigit(int c);
50
53 These macros classify character-coded integer values. Each is a predi‐
54 cate returning non-zero for true, 0 for false. The behavior of these
55 macros, except isascii(), is affected by the current locale (see setlo‐
56 cale(3C)). To modify the behavior, change the LC_TYPE category in set‐
57 locale(), that is, setlocale(LC_CTYPE, newlocale). In the "C" locale,
58 or in a locale where character type information is not defined, charac‐
59 ters are classified according to the rules of the US-ASCII 7-bit coded
60 character set.
61 The isascii() macro is defined on all integer values. The rest are
64 defined only where the argument is an int, the value of which is repre‐
65 sentable as an unsigned char, or EOF, which is defined by the <stdio.h>
66 header and represents end-of-file.
67 Functions exist for all the macros defined below. To get the function
70 form, the macro name must be undefined (for example, #undef isdigit).
71 For macros described with Default and Standard conforming versions,
74 standard-conforming behavior is provided for standard-conforming appli‐
75 cations (see standards(5)) and for applications that define
76 __XPG4_CHAR_CLASS__ before including <ctype.h>.
77 Default
79 isalpha() Tests for any character for which isupper() or islower()
80 is true.
81 Standard conforming
84 isalpha() Tests for any character for which isupper() or islower()
85 is true, or any character that is one of the current
86 locale-defined set of characters for which none of iscn‐
87 trl(), isdigit(), ispunct(), or isspace() is true. In "C"
88 locale, isalpha() returns true only for the characters for
89 which isupper() or islower() is true.
90 isalnum() Tests for any character for which isalpha() or isdigit()
93 is true (letter or digit).
94 isascii() Tests for any ASCII character, code between 0 and 0177
97 inclusive.
98 isblank() Tests whether c is a character of class blank in the cur‐
101 rent locale. This macro/function is not available to
102 applications conforming to standards prior to SUSv3. See
103 standards(5)
104 iscntrl() Tests for any ``control character'' as defined by the
107 character set.
108 isdigit() Tests for any decimal-digit character.
111 Default
114 isgraph() Tests for any character for which ispunct(), isupper(),
115 islower(), and isdigit() is true.
116 Standard conforming
119 isgraph() Tests for any character for which isalnum() and ispunct()
120 are true, or any character in the current locale-defined
121 "graph" class which is neither a space ("") nor a charac‐
122 ter for which iscntrl() is true.
123 islower() Tests for any character that is a lower-case letter or is
126 one of the current locale-defined set of characters for
127 which none of iscntrl(), isdigit(), ispunct(), isspace(),
128 or isupper() is true. In the "C" locale, islower() returns
129 true only for the characters defined as lower-case ASCII
130 characters.
131 Default
134 isprint() Tests for any character for which ispunct(), isupper(),
135 islower(), isdigit(), and the space character ("") is
136 true.
137 Standard conforming
140 isprint() Tests for any character for which iscntrl() is false, and
141 isalnum(), isgraph(), ispunct(), the space character (""),
142 and the characters in the current locale-defined "print"
143 class are true.
144 ispunct() Tests for any printing character which is neither a space
147 ("") nor a character for which isalnum() or iscntrl() is
148 true.
149 isspace() Tests for any space, tab, carriage-return, newline, verti‐
152 cal-tab or form-feed (standard white-space characters) or
153 for one of the current locale-defined set of characters
154 for which isalnum() is false. In the "C" locale, iss‐
155 pace() returns true only for the standard white-space
156 characters.
157 isupper() Tests for any character that is an upper-case letter or is
160 one of the current locale-defined set of characters for
161 which none of iscntrl(), isdigit(), ispunct(), isspace(),
162 or islower() is true. In the "C" locale, isupper() returns
163 true only for the characters defined as upper-case ASCII
164 characters.
165 Default
168 isxdigit() Tests for any hexadecimal-digit character ([0−9], [A−F],
169 or [a−f]).
170 Standard conforming
173 isxdigit() Tests for any hexadecimal-digit character ([0−9], [A−F],
174 or [a−f] or the current locale-defined sets of characters
175 representing the hexadecimal digits 10 to 15 inclusive).
176 In the "C" locale, only
177 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f
179 are included.
181
184 If the argument to any of the character handling macros is not in the
185 domain of the function, the result is undefined. Otherwise, the macro
186 or function returns non-zero if the classification is TRUE and 0 if the
187 classification is FALSE.
188
190 These macros or functions can be used safely in multithreaded applica‐
191 tions, as long as setlocale(3C) is not being called to change the
192 locale.
193
195 See attributes(5) for descriptions of the following attributes:
196 ┌───────────────────────────────────────────────────────────┐
201 │ATTRIBUTE TYPE ATTRIBUTE VALUE │
202 │CSI Enabled │
203 │Interface Stability Standard │
204 │MT-Level MT-Safe with exceptions │
205 └───────────────────────────────────────────────────────────┘
206
208 setlocale(3C), stdio(3C), ascii(5), environ(5), standards(5)
209SunOS 5.11 28 Jan 2005 ctype(3C)