isalnum to isxdigit - Test Integer Value

Syntax

#include <ctype.h>
                              /* test for:                            */
int isalnum(int c);  /* alphanumeric character               */
int isalpha(int c);  /* alphabetic character                 */
int iscntrl(int c);  /* control character                    */
int isdigit(int c);  /* decimal digit                        */
int isgraph(int c);  /* printable character, excluding space */
int islower(int c);  /* lowercase character                  */
int isprint(int c);  /* printable character, including space */
int ispunct(int c);  /* nonalphanumeric printable character, excluding space */
int isspace(int c);  /* whitespace character                 */
int isupper(int c);  /* uppercase character                  */
int isxdigit(int c); /* hexadecimal digit                    */

Description

These functions test a given integer value c to determine if it has a certain property as defined by the LC_CTYPE category of your current locale. The value of c must be representable as an unsigned char, or EOF.

The functions test for the following:

isalnum

Alphanumeric character (uppercase or lowercase letter, or decimal digit), as defined in the locale source file in the alnum class of the LC_CTYPE category of the current locale.
isalpha
Alphabetic character, as defined in the locale source file in the alpha class of the LC_CTYPE category of the current locale.
iscntrl
Control character, as defined in the locale source file in the cntrl class of the LC_CTYPE category of the current locale.
isdigit
Decimal digit (0 through 9), as defined in the locale source file in the digit class of the LC_CTYPE category of the current locale.
isgraph
Printable character, excluding the space character, as defined in the locale source file in the graph class of the LC_CTYPE category of the current locale.
islower
Lowercase letter, as defined in the locale source file in the lower class of the LC_CTYPE category of the current locale.
isprint
Printable character, including the space character, as defined in the locale source file in the print class of the LC_CTYPE category of the current locale.
ispunct
Nonalphanumeric printable character, excluding the space character, as defined in the locale source file in the punct class of the LC_CTYPE category of the current locale.
isspace
White-space character, as defined in the locale source file in the space class of the LC_CTYPE category of the current locale.
isupper
Uppercase letter, as defined in the locale source file in the upper class of the LC_CTYPE category of the current locale.
isxdigit
Hexadecimal digit (0 through 9, a through f, or A through F), as defined in the locale source file in the xdigit class of the LC_CTYPE category of the current locale.

You can redefine any character class in the LC_CTYPE category of the current locale, with some restrictions. See the section about the LC_CTYPE class in the VisualAge C++ Programming Guide for details about these restrictions.

Returns

These functions return a nonzero value if the integer satisfies the test condition, or 0 if it does not.

Example Code

This example analyzes all characters between 0x0 and 0xFF. The output of this example is a 256-line table showing the characters from 0 to 255, indicating whether they have the properties tested for.

#include <stdio.h>#include <ctype.h>
#include <locale.h>

#define UPPER_LIMIT   0xFF

int main(void)
{
   int ch;

   setlocale(LC_ALL, "En_US");

   for (ch = 0; ch <= UPPER_LIMIT; ++ch) {
      printf("%#04x ", ch);
      printf("%c", isprint(ch)  ? ch     : ' ');
      printf("%s", isalnum(ch)  ? " AN"  : "   ");
      printf("%s", isalpha(ch)  ? " A "  : "   ");
      printf("%s", iscntrl(ch)  ? " C "  : "   ");
      printf("%s", isdigit(ch)  ? " D "  : "   ");
      printf("%s", isgraph(ch)  ? " G "  : "   ");
      printf("%s", islower(ch)  ? " L "  : "   ");
      printf("%s", ispunct(ch)  ? " PU"  : "   ");
      printf("%s", isspace(ch)  ? " S "  : "   ");
      printf("%s", isprint(ch)  ? " PR"  : "   ");
      printf("%s", isupper(ch)  ? " U "  : "   ");
      printf("%s", isxdigit(ch) ? " H "  : "   ");
      putchar('\n');
   }
   return 0;

   /****************************************************************************
      The output should be similar to :
      :
      0x20                        S  PR
      0x21 !             G     PU    PR
      0x22 "             G     PU    PR
      0x23 #             G     PU    PR
      0x24 $             G     PU    PR
      0x25 %             G     PU    PR
      0x26 &             G     PU    PR
      0x27 '             G     PU    PR
      0x28 (             G     PU    PR
      0x29 )             G     PU    PR
      0x2a *             G     PU    PR
      0x2b +             G     PU    PR
      0x2c ,             G     PU    PR
      0x2d -             G     PU    PR
      0x2e .             G     PU    PR
      0x2f /             G     PU    PR
      0x30 0 AN       D  G           PR    H
      0x31 1 AN       D  G           PR    H
      0x32 2 AN       D  G           PR    H
      0x33 3 AN       D  G           PR    H
      0x34 4 AN       D  G           PR    H
      0x35 5 AN       D  G           PR    H
      0x36 6 AN       D  G           PR    H
      0x37 7 AN       D  G           PR    H
      0x38 8 AN       D  G           PR    H
      0x39 9 AN       D  G           PR    H
      :
   ****************************************************************************/
}

Related Information

• isascii
  
• iswalnum to iswxdigit
  
• setlocale
  
• tolower - toupper
  
• toascii - _tolower - _toupper

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