Function            midstr - return the middle portion of a string

  Syntax              char *midstr(char *source, int begin, int len);

  Prototype in        stringhk.h

  Remarks             midstr performs just like its BASIC counterpart
                      MID$().

                      midstr returns the middle part of a string.

  Return value        midstr returns the substring of source, using begin
                      as the offset from the beginning to start the
                      substring, for len characters.

                      midstr returns a pointer to the storage location
                      containing the new string, or NULL if space could
                      not be allocated.

  See also            leftstr(), rightstr()

  Example             #include <stringhk.h>
                      #include <stdio.h>            /* for the printf */

                      main()
                      {
                           char msg[25], *m;

                           strcpy(msg,"This is another test");
                           m = midstr(msg,5,7);
                           printf("%s\n",msg);
                           printf("%s\n",m);
                      }

  Program output      This is another test
                      is anot