From: Rob Biedenharn <Rob@...>
Date: 2008-11-23T10:52:11+09:00
Subject: Re: Printing right arrow vs. a sane progressbar library


On Nov 22, 2008, at 8:18 PM, Shot (Piotr Szotkowski) wrote:

> I want to track the progress of a set of (forkoff’d) processes in
> a simple way. What I have in mind is a line of dots equal in length
> to the number of processes, and once a process number X finishes,
> it prints \r, then advances X characters to the right and prints o
> – so after three of eight processes finish, it could look  
> like ..o..oo.
>
> The closest I got is the below (in one line, so easily pastable to  
> IRB):
>
> print '.' * 25; (0...25).sort_by{rand}.each { |n| print "\r"; print  
> "\c[[C" * n; print 'o'; sleep 0.5 }; print "\n"
>
> It seems to work in IRB and in a script (after $stdout.sync = true),
> unless the number of processes is larger than the terminal window’s
> width.
>
> Is this a sane method of doing what I want to do, or does
> it just ‘happens to work’ in GNOME Terminal on my Ubuntu?
>
> Is there a saner way to advance by a char than printing the right  
> arrow?


status='.'*25; print status; (0...25).sort_by{rand}.each{|n|  
status[n]='o'; print "\r#{status}"; sleep(0.1+rand/10.0)};puts

While it still has trouble with more values that screen columns, it  
should be a bit better with race conditions.  You could, perhaps, add  
a clear-to-EOL sequence, too.

-Rob

>
>
> On a similar note: Is there a simple progressbar library for Ruby
> (ideally if itcan be somehow used with forkoff’d processes, but I’m
> aware it’d require some kind of passing of state to the outside of the
> block)?
>
> Is there anything else than Ruby/ProgressBar¹ (say, in a gem…)?
>
> ¹ http://0xcc.net/ruby-progressbar/
>
> (I’m aware the above is prone to a race condition if two processes
> finish at the same time and the second one of them prints its \r
> before the first one prints its o, but let’s disregard this for now.)
>
> -- Shot
> -- 
> If I was to use Bugzilla when I was a tester, I'd quit
> and become a gardener.      -- a Syllable OS developer

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com