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      isalnum

      From cppreference.com
      <c‎ |string‎ |byte
       
       
       
       
      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 ofch is not representable asunsignedchar and is not equal toEOF.

      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 ofisalnum with different locales (OS-specific).

      Run this code
      #include <ctype.h>#include <locale.h>#include <stdio.h> int main(void){unsignedchar 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 0isalnum('\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

      checks if a wide character is alphanumeric
      (function)[edit]
      ASCII valuescharacters

      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–\10control codes (NUL, etc.)≠000000000000
      9\x9\11tab (\t)≠00≠0≠000000000
      10–13\xA–\xD\12–\15whitespaces (\n,\v,\f,\r)≠00≠0000000000
      14–31\xE–\x1F\16–\37control codes≠000000000000
      32\x20\40space0≠0≠0≠000000000
      33–47\x21–\x2F\41–\57!"#$%&'()*+,-./0≠000≠0≠0000000
      48–57\x30–\x39\60–\7101234567890≠000≠00≠0000≠0≠0
      58–64\x3A–\x40\72–\100:;<=>?@0≠000≠0≠0000000
      65–70\x41–\x46\101–\106ABCDEF0≠000≠00≠0≠0≠000≠0
      71–90\x47–\x5A\107–\132GHIJKLMNOP
      QRSTUVWXYZ      		0≠000≠00≠0≠0≠0000
      91–96\x5B–\x60\133–\140[\]^_`0≠000≠0≠0000000
      97–102\x61–\x66\141–\146abcdef0≠000≠00≠0≠00≠00≠0
      103–122\x67–\x7A\147–\172ghijklmnop
      qrstuvwxyz      		0≠000≠00≠0≠00≠000
      123–126\x7B–\x7E\173–\176{|}~0≠000≠0≠0000000
      127\x7F\177backspace character (DEL)≠000000000000
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