isalnum
From cppreference.com
Defined in header <ctype.h>
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int isalnum( int ch ); |
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Checks if the given character is an alphanumeric character as classified by the current C locale. In the default locale, the following characters are alphanumeric:
- Digits (
0123456789
), - Uppercase letters (
ABCDEFGHIJKLMNOPQRSTUVWXYZ
), - Lowercase letters (
abcdefghijklmnopqrstuvwxyz
).
The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.
Contents |
[edit] Parameters
ch | - | character to classify |
[edit] Return value
Non-zero value if the character is an alphanumeric character, 0 otherwise.
[edit] Example
Demonstrates the use of isalnum
with different locales (OS-specific).
Run this code
#include <ctype.h> #include <locale.h> #include <stdio.h> int main(void) { unsigned char c = '\xdf'; // German letter ß in ISO-8859-1 printf("isalnum('\\xdf') in default C locale returned %d\n", !!isalnum(c)); if (setlocale(LC_CTYPE, "de_DE.iso88591")) printf("isalnum('\\xdf') in ISO-8859-1 locale returned %d\n", !!isalnum(c)); }
Possible output:
isalnum('\xdf') in default C locale returned 0 isalnum('\xdf') in ISO-8859-1 locale returned 1
[edit] References
- C23 standard (ISO/IEC 9899:2024):
- 7.4.1.1 The isalnum function (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.4.1.1 The isalnum function (p: 145)
- C11 standard (ISO/IEC 9899:2011):
- 7.4.1.1 The isalnum function (p: 200)
- C99 standard (ISO/IEC 9899:1999):
- 7.4.1.1 The isalnum function (p: 181)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.3.1.1 The isalnum function
[edit] See also
(C95) |
checks if a wide character is alphanumeric (function) |
C++ documentation for isalnum
|
ASCII values | characters |
isalnum |
|||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
decimal | hexadecimal | octal | |||||||||||||
0–8 | \x0 –\x8
|
\0 –\10
|
control codes (NUL , etc.)
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
9 | \x9
|
\11
|
tab (\t )
|
≠0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
10–13 | \xA –\xD
|
\12 –\15
|
whitespaces (\n , \v , \f , \r )
|
≠0
|
0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
14–31 | \xE –\x1F
|
\16 –\37
|
control codes | ≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
32 | \x20
|
\40
|
space | 0
|
≠0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
33–47 | \x21 –\x2F
|
\41 –\57
|
!"#$%&'()*+,-./
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
48–57 | \x30 –\x39
|
\60 –\71
|
0123456789
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
0
|
0
|
0
|
≠0
|
≠0
|
58–64 | \x3A –\x40
|
\72 –\100
|
:;<=>?@
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
65–70 | \x41 –\x46
|
\101 –\106
|
ABCDEF
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
≠0
|
0
|
0
|
≠0
|
71–90 | \x47 –\x5A
|
\107 –\132
|
GHIJKLMNOP QRSTUVWXYZ
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
≠0
|
0
|
0
|
0
|
91–96 | \x5B –\x60
|
\133 –\140
|
[\]^_`
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
97–102 | \x61 –\x66
|
\141 –\146
|
abcdef
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
0
|
≠0
|
0
|
≠0
|
103–122 | \x67 –\x7A
|
\147 –\172
|
ghijklmnop qrstuvwxyz
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
0
|
≠0
|
0
|
0
|
123–126 | \x7B –\x7E
|
\172 –\176
|
{|}~
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
127 | \x7F
|
\177
|
backspace character (DEL )
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|