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

Character Type Macros and Functions

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