isalnum -- Alphanumeric Character Test


SYNOPSIS
#include <ctype.h>
int isalnum(int c);
DESCRIPTION
isalnum
tests an integer value to determine whether it is an
alphabetic (uppercase or lowercase) or numeric character.
RETURN VALUE
isalnum
returns 0 if the character is not alphanumeric, or a nonzero
value if it is alphanumeric. If the argument is EOF
, 0 is returned.
CAUTIONS
The effect of isalnum
on a noncharacter argument other than EOF
is undefined. Do not assume that isalnum
returns either 0 or 1.
EXAMPLE
#include <ctype.h>
#include <stdio.h>
#define MAXLEN 40
main()
{
char id[MAXLEN+1];
int i;
char *text;
char input[MAXLEN];
puts("Enter a string of characters (40 at most).");
text = gets(input);
puts("Initial alphanumeric characters you entered are:");
for (i = 0; i < MAXLEN && isalnum(text[i]); i++) {
id[i] = text[i];
putc(id[i]);
}
id[i] = '0';
putc('n');
}
RELATED FUNCTIONS
isalpha
, isdigit
SEE ALSO