{{keywords>wiki library source code example reference}}
===== isalnum =====
<code c>
    int isalnum(int chr);
</code>
check if a character Alphanumeric

===== C Sourcecode Example =====
<code c>
#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */

#include <ctype.h>

int main ()
{
  int i;
  char string[11]="Test -!&%1";
  for (i=0; i <= 11;i++)
    {
     if ( isalnum(string[i]) != 0 )
      {
       printf("Character %i is alphanumeric\n",i);
      }
    }
  return 0;
}
</code>
==== output ====
    user@host:~$ ./isalnum 
    Character 0 is alphanumeric
    Character 1 is alphanumeric
    Character 2 is alphanumeric
    Character 3 is alphanumeric
    Character 9 is alphanumeric