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Posted by xhoster on June 5, 2008, 3:38 pm
Please log in for more thread options > I found the following demo in a book regarding usage of "select" ...
>
> 1 select(FH1);
> 2 print "goes to FH1.\n";
> 3
> 4 $TempHandle = select(FH2);
> 5 print "goes to FH2.\n";
> 6
> 7 select ($TempHandle);
> 8 print "goes to FH1.\n"
>
> This is in Perl for Dummies, 4th ed, p182.
>
> My questions are:
>
> It seems if I need to verify this, would need to add the following in
> the pl file?
>
> open(FH1, '>print1.txt');
> open(FH2, '>print2.txt');
Yes, and you should check those opens for failure.
>
> Line 5 would still uses FH1 and goes into print1.txt, as FH2 has not
> been selected;
Hunh? The selection of FH2 is in line 4, so why hasn't it been executed?
Unless you are refering to line 5 of some hypothetical program which has
its lines renumbered because of the insertion of the open statements, in
which case you would have to show us that program.
> and line eight will uses $TempHandle or FH2 and goes
> into print2.txt, as FH2 is is now selected through $TempHandle
> assignment?
$TempHandle holds FH1, not FH2. single-argument select selects the new
file handle (FH2 on line 4) and returns the old, previously selected, file
handle (FH1 on line 4, into $TempHandle)
> However, my understanding contradicts to the suggestions in the book,
> such as line 5 would goes in print2.txt, and line 8 would goes in
> print1.txt. My verification also says the author is correct.
>
> What's wrong with me?
I think you understand the select backwards.
Xho
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