1ISALPHA(3)                 Linux Programmer's Manual                ISALPHA(3)
2
3
4

NAME

6       isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower,
7       isprint, ispunct, isspace,  isupper,  isxdigit,  isalnum_l,  isalpha_l,
8       isascii_l,  isblank_l,  iscntrl_l, isdigit_l, isgraph_l, islower_l, is‐
9       print_l, ispunct_l, isspace_l, isupper_l, isxdigit_l - character  clas‐
10       sification functions
11

SYNOPSIS

13       #include <ctype.h>
14
15       int isalnum(int c);
16       int isalpha(int c);
17       int iscntrl(int c);
18       int isdigit(int c);
19       int isgraph(int c);
20       int islower(int c);
21       int isprint(int c);
22       int ispunct(int c);
23       int isspace(int c);
24       int isupper(int c);
25       int isxdigit(int c);
26
27       int isascii(int c);
28       int isblank(int c);
29
30       int isalnum_l(int c, locale_t locale);
31       int isalpha_l(int c, locale_t locale);
32       int isblank_l(int c, locale_t locale);
33       int iscntrl_l(int c, locale_t locale);
34       int isdigit_l(int c, locale_t locale);
35       int isgraph_l(int c, locale_t locale);
36       int islower_l(int c, locale_t locale);
37       int isprint_l(int c, locale_t locale);
38       int ispunct_l(int c, locale_t locale);
39       int isspace_l(int c, locale_t locale);
40       int isupper_l(int c, locale_t locale);
41       int isxdigit_l(int c, locale_t locale);
42
43       int isascii_l(int c, locale_t locale);
44
45   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
46
47       isascii():
48           _XOPEN_SOURCE
49               || /* Glibc since 2.19: */ _DEFAULT_SOURCE
50               || /* Glibc <= 2.19: */ _SVID_SOURCE
51
52       isblank():
53           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
54
55       isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(),
56       isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(),
57       isupper_l(), isxdigit_l():
58           Since glibc 2.10:
59               _XOPEN_SOURCE >= 700
60           Before glibc 2.10:
61               _GNU_SOURCE
62
63       isascii_l():
64           Since glibc 2.10:
65               _XOPEN_SOURCE >= 700 && (_SVID_SOURCE || _BSD_SOURCE)
66           Before glibc 2.10:
67               _GNU_SOURCE
68

DESCRIPTION

70       These  functions  check  whether c, which must have the value of an un‐
71       signed char or EOF, falls into a certain character class  according  to
72       the  specified  locale.   The functions without the "_l" suffix perform
73       the check based on the current locale.
74
75       The functions with the "_l" suffix perform the check based on  the  lo‐
76       cale  specified  by  the  locale  object locale.  The behavior of these
77       functions is undefined if locale is the special locale object  LC_GLOB‐
78       AL_LOCALE (see duplocale(3)) or is not a valid locale object handle.
79
80       The list below explains the operation of the functions without the "_l"
81       suffix; the functions with the "_l" suffix differ only in using the lo‐
82       cale object locale instead of the current locale.
83
84       isalnum()
85              checks for an alphanumeric character; it is equivalent to (isal‐
86              pha(c) || isdigit(c)).
87
88       isalpha()
89              checks for an alphabetic character; in the standard "C"  locale,
90              it  is  equivalent  to  (isupper(c) || islower(c)).  In some lo‐
91              cales, there may be additional characters for which isalpha() is
92              true—le