#include <ctype.h>

void trim(char *str)
{
  char *last = NULL,            /* last non-space character */
       *next,                   /* next character to write to */
       *itr;

  for (next = str, itr = str; *itr != '\0'; ++itr)
  {
    *next = *itr;
    if (!isspace((unsigned char) (*itr)))
      last = next;
    if (last != NULL)
      ++next;
  }

  if (last == NULL)
    *next = '\0';
  else
    *(last + 1) = '\0';
}