Re: Speaking of "coproc" ...

["Bart Schaefer" <schaefer@brasslantern.com>]

On May 5, 10:02am, Andrew Main wrote:
} Subject: Re: Speaking of "coproc" ...
}
} Bart Schaefer wrote:
} >How does one close the input to the coproc, so as to send it an end-of-file?
} >The only thing I've come up with is "coproc exit" which seems rather silly
} >and which closes both the input and the output.
} 
} Coprocesses are a bit of a mess.  I'd like to make it possible to attach
} the coprocess to specified fd numbers, just like file redirections,

That's easily accomplished already, by e.g. 3<&p or 4>&p.  The odd bit is
that when ksh does >&p, it -closes- the "p" descriptor after dup'ing it.
When zsh does >&p, it leaves "p" open, so you can do >&p again to the same
coprocess.  (This is not true of <&p, which makes me think >&p has a bug.)

This has some interesting side effects, one of which is that there's no
way to explicitly close down the coproc input (except to start another).

} so that one could close either pipe with the ">&-" syntax.  This would
} also make it possible to have multiple independent coprocesses.

That's also already possible, as someone on the zsh-users thread pointed
out.

	coproc first-coproc
	exec 3<&p 4>&p
	coproc second-coproc
	exec 5<&p 6>&p
	coproc etcetera

} To do this properly I think we'd need an extended redirection syntax,
} to allow redirecting file descriptors of more than one digit

That's completely orthogonal.

} perhaps we could do something like the rc syntax?

I don't know what that is.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com