The "loop and a half"

[Peter J. Holzer]

On 2017-10-06 11:41, bartc <bc at freeuk.com> wrote:
> On 06/10/2017 12:04, Rhodri James wrote:
>> On 05/10/17 19:45, bartc wrote:
>>> Yes, I tried typing 'sort' in Linux, where it apparently hangs (same 
>>> on Windows actually). The reason: because it might have killed someone 
>>> to have added a message saying what you are expected to type and how 
>>> to end it. (Namely, press Ctrl-D start at the start of a line in 
>>> Linux, and Ctrl-Z followed by Enter, I think also at the start, in 
>>> Windows.)
>> 
>> Actually it might.  Linux tools are written not to assume that stdin and 
>> stdout are the console, because they frequently aren't.  Extra puff 
>> written to stdout at best makes it harder to use in a pipeline, and at 
>> worst makes it useless; tools that do that tend not to get used.
>
> A lot of people aren't getting it.
>
> The internal utilities used within an operating system, primarily 
> intended for file or redirected i/o with no live interaction, should be 
> distinct from those designed to be used directly with a live user.
>
> Or is it against the rules of Unix to have two different versions of a 
> program?
>
> Then you might have 'sort' for the non-interactive version, and 'isort' 
> or whatever for the interactive.

How would that stop your clueless user from invoking sort and thinking
that it hangs? Short of putting it into /usr/lib or so, but that would
make it hard to use in a pipe. 

I can see some merit in the idea that filters could print a short help
message when reading from a terminal, but creating a second
"interactive" version of each filter with a different name seems to be
utterly pointless to me.

        hp


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