SAS/C Library Reference, Vol. 1

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