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Re: wc command

From: Jim Meyering
Subject: Re: wc command
Date: Mon, 22 Dec 2008 18:57:29 +0100

Pádraig Brady <address@hidden> wrote:
> Eric Blake wrote:
>> According to Andrew McGill on 12/22/2008 1:38 AM:
>>> My guess is that while it would be friendly to provide a similar message for
>>> wc (od, head, tail, etc), it would violate something posixy (and is 
>>> therefore
>>> imposixable).
>> It would be possible to add a conditional check, where if POSIXLY_CORRECT
>> is not defined in the environment and a filter app is started with a tty
>> as stdin and stderr (ie. the same criteria for what POSIX requires bash to
>> use for whether a shell is interactive), then we issue a warning to
>> stderr.  Normally, we don't like adding additional uses of
>> POSIXLY_CORRECT, but this particular idea may help stave off confusion.
>> Care to write such a patch?  It would need to be applied to all of the
>> coreutils that can act as a filter, not just wc.
> So you're proposing something like:
> if (!POSIXLY_CORRECT && isatty(0) & isatty(2))
>     fprintf(stderr,"Please enter your text now, or Ctrl-d to end\n");
> While logically correct, I'm not sure such a patch would
> be that useful/desired. More code and more translations,
> for something that should be quite obvious.
> The OP entered `wc` accidentally, so it's not as if
> they were confused about the way the filter operated.
> 99.999999999999999% of cases like this would be users
> wait a while, and go "oops", Ctrl-c.
> I'm all for helping new users, and giving meaningful
> error messages, but I'm not sure the gain is worth the
> effort of updating all filters.
> I'm 40:60 for this proposal.

I too would prefer not to introduce
such new tests of POSIXLY_CORRECT.

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