Re: grep-use-null-device

[Emilio Lopes <eclig@gmx.net>]

Emilio Lopes writes:

> As a result, if I forget to provide a filename to "M-x grep" it will
> run forever, waiting for me to kill it.

Richard M Stallman writes:

>     So, my grep program supports "-H" but it apparently has not the
>     expected semantics.

> That is a very vague statement.  It tells us nothing.

No, no.  It's very concrete if you consider the rest of the message,
which you didn't quote.  Anyway, I understand the problem better now.

If the user forgets to provide a filename to "M-x grep" (as in
"grep -nH foo") it will run indefinitely waiting for input from
stdin until killed.  In such cases it's useful to have `null-device'
appended, even if the grep program supports the option "-H" (which
has an other purpose anyway).

One could even argue if Emacs should not append *two* instances of
`null-device', in the case the use just press enter at the grep prompt
without even typing a regexp.