Chapter Contents

Previous

Next
isdigit

isdigit



Test for Numeric Character

Portability: ISO/ANSI C conforming, UNIX compatible


SYNOPSIS
DESCRIPTION
RETURN VALUE
CAUTION
EXAMPLE
RELATED FUNCTIONS
SEE ALSO


SYNOPSIS

#include <ctype.h>

int isdigit(int c);


DESCRIPTION

isdigit tests an integer value to determine whether it is a numeric character (digit).


RETURN VALUE

isdigit returns 0 if the character is not a digit, or a nonzero value if it is. If the argument is EOF , 0 is returned.


CAUTION

The effect of isdigit on a noncharacter argument other than EOF is undefined. Do not assume that isdigit returns either 0 or 1.


EXAMPLE

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

#define IDMAX 40

main()
{
   char id[IDMAX+1];
   char *text;
   char input[IDMAX];
   int i;

   puts("Enter a string of numbers/characters (maximum 40):");
   text = gets(input);

      /* Copy a string of digits from text to id. */
   for (i = 0; i < IDMAX && isdigit(text[i]); ++i)
      id[i] = text[i];

   id[i] = '\0';
      /* Only the digits should be copied. */
   printf("You first entered these digits: %s\n", id);
}


RELATED FUNCTIONS

isxdigit


SEE ALSO


Chapter Contents

Previous

Next

Top of Page

Copyright © 2001 by SAS Institute Inc., Cary, NC, USA. All rights reserved.