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isalnum

From cppreference.com
< c‎ | string‎ | byte
 
 
 
Null-terminated byte strings
Functions
Character manipulation
Conversions to and from numeric formats
(C23)(C23)(C23)
String manipulation String examination Memory manipulation Miscellaneous
 
Defined in header <ctype.h>
int isalnum( int ch );

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) [edit]
C++ documentation for isalnum
ASCII values characters

iscntrl
iswcntrl

isprint
iswprint

isspace
iswspace

isblank
iswblank

isgraph
iswgraph

ispunct
iswpunct

isalnum
iswalnum

isalpha
iswalpha

isupper
iswupper

islower
iswlower

isdigit
iswdigit

isxdigit
iswxdigit

decimal hexadecimal octal
0–8 \x0–\x8 0円–10円 control codes (NUL, etc.) ≠0 0 0 0 0 0 0 0 0 0 0 0
9 \x9 11円 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0
10–13 \xA–\xD 12円–15円 whitespaces (\n, \v, \f, \r) ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
14–31 \xE–\x1F 16円–37円 control codes ≠0 0 0 0 0 0 0 0 0 0 0 0
32 \x20 40円 space 0 ≠0 ≠0 ≠0 0 0 0 0 0 0 0 0
33–47 \x21–\x2F 41円–57円 !"#$%&'()*+,-./ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
48–57 \x30–\x39 60円–71円 0123456789 0 ≠0 0 0 ≠0 0 ≠0 0 0 0 ≠0 ≠0
58–64 \x3A–\x40 72円–100円 :;<=>?@ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
65–70 \x41–\x46 101円–106円 ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0
71–90 \x47–\x5A 107円–132円 GHIJKLMNOP
QRSTUVWXYZ 		0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
91–96 \x5B–\x60 133円–140円 [\]^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
97–102 \x61–\x66 141円–146円 abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0
103–122 \x67–\x7A 147円–172円 ghijklmnop
qrstuvwxyz 		0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
123–126 \x7B–\x7E 173円–176円 {|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
127 \x7F 177円 backspace character (DEL) ≠0 0 0 0 0 0 0 0 0 0 0 0

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