Read infinite Loop

[lynargs]

Hello,

I have 1 physical file with 4 entries. Im reading this file with DOW not %eof and a read but i stuck at the first record and it goes to a infinite loop.
I dont know why and how can i get to the next entry ? i tried it with iter but doesnt work.

/free                  
 Read TEST;           
   dow not %eof;       
   do something          
   ExSr $testsr;        
   enddo;              
 *inlr=*on;            
/end-free              
Endsr;

[jtaylor___]

Your only read is outside your loop, so it never reads more than one row.

[JonBoy]

When you use this technique (often referred to as a priming read), you also need to be sure to include a read _within_ the loop. in this case it should precede the enddo.

[lynargs]

Ok i just solved the problem but then i look at my output the programm reads the last record twice. How can i solve this ?

[Scott M]

What does your code look like now so we can help?

[Vectorspace]

Hard to say when we don't know what you changed your code to. Can you share the updated code?

Personally I prefer this to a priming read:

DoU %EOF(TEST);
  Read TEST;
  If %EOF(TEST);
    Leave;
  EndIf;
  // do something

EndDo;

That way there is only one line where the record is read. It's not as big an issue with native IO, but in SQL the equivalent to a READ is a FETCH statement, which can be a lot larger than "READ x"

P.S. you should always include the filename in %FOUND and %EOF, as in my example. Otherwise it merely refers to the last IO operation performed. So if somewhere within //do something you were doing another READ on another table, it could affect TEST's loop

[JonBoy]

Interesting. I dislike this method because it makes it harder to differentiate between first read and subsequent. EOF on first read is probably/possibly an error (i.e. empty input file). But on all other reads it is an expected condition. with your approach it is much harder to differentiate the two. I should not that I invariably add a comment

// Loop priming read

Or something similar to warn those who use your technique.