Re: [Gnu-arch-users] tla & user interactivity

[Aaron Bentley]

David Allouche wrote:

> > I've been writing a mini tla-colorizer.  This works fine for 
> > non-interactive commands, and works quite badly for interactive ones.
> >
> > So far, commit is the only potentially-interactive command in tla that 
> > I'm aware of.  

> > Are there other interactive tla commands commands I should be aware of?
>
>
> Virtually all commands which access archives can end up being
> interactive: ssh or gpg asking for a password/passphrase, though that
> would probably not be a problem in your case.

Hoo boy.  That's pretty pathological.  My ssh keys are in ssh-agent, and
I don't sign my archive, but...

> That, and the fact that piping w/o merging stdout and stderr may cause
> messages to be printed on the user terminal in the wrong order, because
> of buffering in the pipe, which is impossible by design to work around.
> However, whether that can be a problem practically remains to be seen.

So far, it hasn't been a problem, but I can see it could be.  But
everyone filters stdout this way.

> If you are bound to implement this colorization feature the Right Way, I
> believe it would be necessary for tla to provide a hook. For example,
> it could check for a TLA_COLORIZER environment variable, the name of the
> colorizer executable, and use it as a coprocess to filter its output, to
> the exclusion of the output of sub-process (authentication) and allowing
> proper stream merging with dup2(2).

OOH, how 'bout a hackerlab colorizer handler?  Then chatter_fd could be
different from stdout (or /dev/null).

> Some additional protocol could be used to colorize stdout and stderr
> differently while preserving synchronization. I am not sure what is the
> best way to do it, but you could just pipe everything through the
> colorizer stdin (for synchronization) and use one control char to toggle
> a bit between stdout/stderr (for different colorization and demuxing).

I guess another option would be a colorizing wrapper that handled stderr
and stdout as separate file descriptors.

> But if you are in Worse is Better mode, please just disregard this
> message entirely.

I am in Worse is Better mode.  Current versions of aba support an
abafilter (should probably be uppercase) variable.  If present, the
specified command is used as a pipe for non-interactive commands.

But I won't disregard your message, because it's important to know how
it would be done The Right Way.  Thanks for the insight.

Aaron

--
Aaron Bentley
Director of Technology
Panometrics, Inc.