Re: \prompt for psql

I have applied a modified version of your patch. I moved the prompt
'text' field as optional before name, and removed the default prompt
string, which seemed un-Unix-like.

I also simplified when stdin/stdout is used. If stdin is the terminal,
it seems it makes no difference if we use the terminal or stdin. Now,
prompt uses the terminal unless -f is used. I think this simplifies its
behavior. I realize cases where stdin is the terminal and stdout is not
behave differently in the new patch (prompt goes to the terminal and not
to stdout), but I think the previous behavior was too confusing to be
useful. I can adjust this if people want different behavior.

Update version attached.

---------------------------------------------------------------------------

Chad Wagner wrote:
> On 2/17/07, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >
> > "Chad Wagner" <chad(dot)wagner(at)gmail(dot)com> writes:
> > > Would it make sense to say:
> > > 1. if pset.notty is set and '-f' switch is not set then use
> > simple_prompt
> > > 2. else then use gets_fromFile(stdin) <or some other alternative?>
> >
> > Actually, there's another issue, which is where to send the prompt.
> > If we're using /dev/tty the answer is clear, but if we're proposing to
> > read from stdin then it's not necessarily the case that stdout (or even
> > stderr) is appropriate.
> >
> > Arguably a prompt is useless except to a human user, so maybe the rule
> > is "if stdin is a tty according to pset.notty, then prompt to /dev/tty;
> > otherwise suppress the prompt altogether". Or we could prompt to stderr
> > instead of /dev/tty in this case. I'm not sure if there are plausible
> > use-cases where stdin leads to the terminal and stderr doesn't.
> >
>
> pset.notty will be set to 1 if either stdin or stdout is not a tty. So in
> the case where they are redirecting both input and output then it will
> prompt on /dev/tty, otherwise the prompt would go out on stdout.
>
> I was thinking perhaps it should look at the '-q' quiet switch for
> determining whether to display prompt at all. So perhaps with a '-q' switch
> instead of dumping the prompt to stdout it should always be sent to
> /dev/tty. Also, I think in general most users of this feature that would be
> "scripting" output (via expect or similar) would probably just use the '-v'
> switches.
>
> BTW, attached is the latest version of this patch that includes the code
> (and updates to the psql-ref.sgml) I talked about earlier. Not sure if
> gets_fromFile is favored, or perhaps the creation of a psql_prompt_var
> routine that takes into account some of what simple_prompt is doing but
> considering the logic we are discussing.

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://www.enterprisedb.com

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