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From: reino@cs.eur.nl (Reino de Boer)
Newsgroups: comp.lang.pascal
Subject: Re: Find File?
Message-ID: <1991Feb15.112843.13779@cs.eur.nl>
Date: 15 Feb 91 11:28:43 GMT
References: <1129@tesla.njit.edu> <91042.205829SPRAGGEJ@QUCDN.QueensU.CA>
Reply-To: reino@cs.eur.nl
Organization: Erasmus University Rotterdam
Lines: 47

In <91042.205829SPRAGGEJ@QUCDN.QueensU.CA> SPRAGGEJ@QUCDN.QueensU.CA (John G. Spragge) writes:

>Regarding a question about how to check and see if a file exists:

>There are two methods. The first is to try and open the file with
>Pascal run-time I/O error halting turned off. This is set by the
>$I switch; thus, if you include {$I-} in your file, an attempt
>to open the file will not halt the program. To see whether the file
>was opened successfully, use the IORESULT function.

Assuming you mean something like

function exists( filename : pathstr ) : boolean;
	var 	f : file;
	begin
		assign( f, filename );
		{$I-}
		reset( f );
		{$I+}
		if ioresult = 0 then begin
  			{ file exists }
			close( f );
			exists := true
		end
		else
  			{ file doesn't exist }
			exists := false
	end;

This method can fail for two reasons:
1.  	in old versions of Turbo Pascal
		exists( 'con' ) 
	gives an incorrect result, because it's explicitly of type text.
	But, more importantly:
2.	the file is not found if it's a read-only file on a network
	drive. This is because untyped files (and any other non-text files)
	are opened in update mode by reset( .. ).

>The second method is to use the FINDFIRST command.

And be sure to check whether it is a volume-label, directory, or file.

Hope this helps -- Reino
-- 
Reino R. A. de Boer     "We want to build the right product right, right?"
Erasmus University Rotterdam ( Informatica )
e-mail: reino@cs.eur.nl