Catching Runtime Errors

[mcindafizzy]

I am a rather new programmer and I am currently working on a database driven quiz/game application. I have a need to catch the Runtime error that occurs when a the program tries to open a file that doesn't exist. Unfortanetly I just can't find any documentation on how to catch runtime errors, and therefore I am here. Thanks

 

[Glenn9999]

You need to switch off IO checking when you do your reset then check IOResult.

Like:

assign(file1, 'xxxx.dat');
{$I-}
reset(file1);
{$I+}
if IOResult <> 0 then
begin
writeln('I can not find my data file, terminating!');
halt(10);
end;

 

[lionelhill]

note that (so far as I know) IOresult is reset to zero when you check it (similar behaviour to doserror), so if you need to check it twice, you have to assign its value to a variable and check the variable twice.

 

[stackdump]

A simpler solution in some compilers (such as FPC for example) is the FileExists function, this works like this;

IF FileExists(myfile) THEN carry on ELSE its an error

As far as I know this is actually the same code as Glenn's example but in a ready built function.

 

[TheElusiveYak]

if u are useing 7.0 the fsearch function is useful so a function like this would work, needs the dos unit

uses dos;
function fileexist(filename : string):boolean;
var
s : pathstr;
begin
s := fsearch(filename,getenv('PATH'));
if s = '' then
fileexist := false
else
fileexist := true;
end;