C Trim

#include <ctype.h>
#include <string.h>

#define NUL '\0'

char *trim(char *str)
{
      char *ibuf = str, *obuf = str;
      int i = 0, cnt = 0;

      /*
      **  Trap NULL
      */

      if (str)
      {
            /*
            **  Remove leading spaces (from RMLEAD.C)
            */

            for (ibuf = str; *ibuf && isspace(*ibuf); ++ibuf)
                  ;
            if (str != ibuf)
                  memmove(str, ibuf, ibuf - str);

            /*
            **  Collapse embedded spaces (from LV1WS.C)
            */

            while (*ibuf)
            {
                  if (isspace(*ibuf) && cnt)
                        ibuf++;
                  else
                  {
                        if (!isspace(*ibuf))
                              cnt = 0;
                        else
                        {
                              *ibuf = ' ';
                              cnt = 1;
                        }
                        obuf[i++] = *ibuf++;
                  }
            }
            obuf[i] = NUL;

            /*
            **  Remove trailing spaces (from RMTRAIL.C)
            */

            while (--i >= 0)
            {
                  if (!isspace(obuf[i]))
                        break;
            }
            obuf[++i] = NUL;
      }
      return str;
}