From: Peter Heslin (Peter.Heslin at domain ucd.ie)
Date: Tue 02 May 2000 - 18:46:55 IST
On Tue, May 02, 2000 at 03:45:57PM +0100, Dave O Connor wrote:
> That'd ouput the return value from that nasty shell command, which you don't
> really want. A slightly more efficient (resourcewise, anyway) would be
> something like:
>
> sub num_users
> {
> open(USERS,"/usr/bin/users|");
>
> my $users = <USERS>;
>
> close USERS;
>
> my at domain userlist = split(/\s+/,$users);
>
> my at domain uniqlist;
>
> foreach ( at domain userlist)
> {
> if (!grep($_, at domain uniqlist))
> {
> push( at domain uniqlist,$_);
> }
> }
>
> return scalar at domain uniqlist;
> }
Same idea:
perl -e 'print "There are ", scalar keys %{{map {$_ => 1} split " ", `users`}}, " users logged in.\n"'
Hashes are useful for finding unique elements in a list.
Peter
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