What is wrong with this program

[William T. McGarry]

<  Why does printf insist that data->ut_line is a null string while
<  putchar can display all of the characters of this array?
<  
<  Sorry if this is a trivial question, but it beats the hell 
<  out of me.


The problem with this program is the way in which "data" is defined 
and used:

	struct	utmp	*data;

This only defines that "data" is to be a pointer to a structure with
the format of "utmp".  It does not allocate any space for the structure
itself.  You have to either:

1. Do a malloc right after the open the file -

	data = (struct utmp *) malloc(sizeof(struct utmp));


2. Since "utmp" is such a small structure, a malloc is problably not
   even needed.  Instead, write it like this:

	struct	utmp	data;

   which does allocate space for the structure.  In this case, the "fread"
   call should read into "&data" rather than "data" and all of the lines
   such as "data->ut_line" should be changed to "data.ut_line"
   and change all of the lines from "utmp->ut_line" to "utmp.ut_line"
   and the "fread" call should read into "&data".


Both of these methods work fine on my Fortune 32:16.


Hope this helps!


					Bill McGarry
					decvax!ittatc!bunker!wtm