Meriwether Lewis wrote:
> Hi Gurus!
>
> I have the following sub which creates a random
> string. Each time I call the sub in my perl
> script it returns a random string which is fine.
> The problem is every time I run the script the
> same strings are returned. I'm running perl
> 5.001 on Windows 2000.
>
> sub RandomStr
> {
> my $i=0;
> my $str="";
> foreach(0..9,a..z,A..Z)
> { $i++;
> $arr[$i]=$_
> }
> for($j=0;$j<rand(30);$j++)
> {
> $str.=$arr[rand(58)+1]
> }
> return $str;
> }
>
> So if I run my script calling the above three
> times I get:
>
> brLNh
> 96
> x9k
>
> If I run it again I get the same three strings.
> Why?
Perl tries to 'seed' its random number generator from various
system values to make it different each time. Its first attempt
is to read a value from the system device /dev/urandom which
will be used if the read is successful. Clearly this isn't working
properly in your case so perhaps your urandom device is
misbehaving?
An alternative is that you may incorrectly be calling 'srand' to
seed the random number generator. If you pass a constant
to this function then the random number sequence will be
the same each time.
> Is there a better way to get a random string?
If this suits your purpose, then no. You code could be a lot
better laid out though. Take a look at this for inspiration:
sub RandomStr {
my $str;
my @arr = (0..9, a..z, A..Z);
$str .= $arr[rand(@arr)] for 1 .. rand(30);
$str;
}
HTH,
Rob
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