Re: [bug-gawk] in-place edit request

[Andrew J. Schorr]

On Wed, Dec 26, 2012 at 10:42:44PM +0200, Eli Zaretskii wrote:
> If this is about having 'print', 'printf' etc go to some other file in
> some suitably marked portion of an Awk program, why manipulate stdout
> at all? why not just introduce a command that would make 'print'
> etc. use a stream that is different from stdout, a stream that is
> connected to the file where you want the output to go?  Then you won't
> have any problems restoring stdout in the first place.

Yes -- that's how other programs such as perl and sed accomplish this.  But in
order to take this approach, I think we would have to follow one of two paths:

1. Add a new non-standard built-in awk function to select the output
destination for print and printf statements.

2. Add an extension API hook that would allow an extension to install such
a function.

As discussed previously, I believe there's an existing set_gawk_output function
that probably does what we want, but it is currently used only by the debugger
and is not exposed for other purposes.

I think that's a perfectly reasonable approach, but I think there's a desire to
avoid touching the main gawk source to support this feature.  Since it may be
difficult to implement in-place editing in a thoroughly robust way, it might
not make sense to alter the main gawk source code in an attempt to support
this.

If we want to implement in-place editing entirely inside an extension library,
I think we must resort to manipulating stdout.

Regards,
Andy