"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.
-Josh
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