Re: [PLUG] EOF

[Jeff Abrahamson <jeff@purple.com>]

On Fri, Jan 18, 2002 at 02:03:24PM -0500, Michael C. Toren wrote:
> paul@dpagin.net wrote:
> > > I'm using Linux to program C, however, when I try to do something like (
> > > c = getchar() ) != EOF
> 
> Do you have 'c' defined as a char, or as an int?  getchar() returns an
> int rather than a char, using the high bits to indicate error conditions
> such as EOF, and the lower bits to hold the value of valid data returned.
> 
> gr@eclipsed.net wrote:
> > Have you tried using '^V^D' there instead of literally typing out
> > EOF? (That's control-V control-D. ^V makes the subsequent control
> > character visible.)
> 
> In this context, EOF is a conditioned returned by read(), not a character.
> (It's perfectly valid to read ASCII character 4, ^D, from a file).

Correct (well, s/read/getchar/), and important. Control-D, control-Z,
etc. are end of input indicators to that particular shell. Note that
you can change it using stty, for example, and your programs need know
nothing (because it doesn't affect them).


> > EOF is #defined in a system include somewhere which you're probably
> > not including in your source. Figuring out which include file would
> 
> EOF is defined in stdio.h, along with getchar() and friends.  (If it
> wasn't defined, cc wouldn't be compiling the code in the first place)

Is c a char or an int? GETS(3) defines

    int getchar(void);

for the very good reason that you have to be able to return all valid
char's, and then also something called EOF.

-- 
 Jeff

 Jeff Abrahamson  <http://www.purple.com/jeff/>

 The Big Book of Misunderstanding, now in bookstores and on the web:
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