[EMAIL PROTECTED] wrote:
"John W. Kennedy" <[EMAIL PROTECTED]>
08/01/2005 04:46 PM
To
[EMAIL PROTECTED]
cc
[email protected]
Subject
Re: randomly choosing a file
[EMAIL PROTECTED] wrote:
"John W. Kennedy" <[EMAIL PROTECTED]>
[EMAIL PROTECTED] wrote:
I know how to and can successfully open a directory , but i need to
choose
a file within the directory at random to verify the data on. does anyone
have any suggestions of how to do this? i'm thinking it could take a
while
to create an array of the file names and then randomly pick a slot
there,
but that;s all i can think of right now.
Unfortunately, this is not likely to do you any good, because you need
to know the value of n before starting, and the correct value can be
obtained only by reading the directory in the first place. So....
my @entries;
opendir MYDIR, $directory;
while (my $entry = readdir MYDIR) {
next if -d "$directory/$entry";
push @entries, $entry;
}
closedir MYDIR;
my $chosenfile = @entries[int rand ($#entries + 1)];
this looks like a more efficient variation upon what i was thinking. i
have one question though.. the array starts at 0 for an index, doesn't
$#var give one less than the element in the array since it uses the last
index in the array? wouldn't this mean one wants to *1 to make an
integer
instead of +1 and make the result 1 to [one-greater-than-array] ?
If there are ten directory entries, then $#entries will be 9, and
$#entries+1 will be 10. rand(10) yields 0 <= rand < 10. That truncates
to 0 <= rand <= 9.
John-
that makes sense now. for some reason i was thinking it was 0<= rand <= n
shifted to 1 <= rand <= n. while i have fixed that, i am still getting a
concatination error. I dont quite understand why it is not pulling the
file. it gives me this when i try choosing the file the line before as
well.
I think you'll have to give your exact code and the exact error message.
--
John W. Kennedy
"You can, if you wish, class all science-fiction together; but it is
about as perceptive as classing the works of Ballantyne, Conrad and W.
W. Jacobs together as the 'sea-story' and then criticizing _that_."
-- C. S. Lewis. "An Experiment in Criticism"
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