Subject: bug#19240: cut 8.22 adds newline

From: Eric Blake <[email-masked]>
Date: Mon, 01 Dec 2014 16:06:11 -0700

On 12/01/2014 03:06 PM, Pádraig Brady wrote:

> BTW the argument that it's not a text file is a bit beside the point
> as POSIX also says text files can't contain NUL chars, but we process
> this just fine:
> 
>   $ printf 'a\000b' | cut -c3
>   b

The fact that GNU offers an extension where we gracefully handle NUL
bytes is a bonus of GNU, and does not change the fact that POSIX already
says we are in unspecified territory and can do whatever we deem most
useful.  I suspect that in multibyte locales with non-character encoding
errors, the behavior becomes harder to pinpoint on what makes the most
sense - but again, that is another aspect that makes a file binary
rather than text and therefore falls under unspecified behavior.

> Also comparing other tools like uniq we have:
> 
> solaris> printf '1' | uniq
> solaris> (nothing output!)
> 
> freebsd> printf '1' | uniq
> 1freebsd>
> 
> coreutl> printf '1' | uniq
> 1
> coreutl>

What about:
printf '1\n1' | uniq

GNU treats the two lines as identical (and thus supplied a missing \n on
the second line); but I don't have ready access to test the other two as
I type this.

> If we were just implementing now, I'd not output the extra '\n',
> but changing at this stage needs to be carefully considered,
> and with all the textutils, not just cut(1).

I tend to go the opposite - producing text output, even on non-text
input, is more likely to be useful when piping files to other utilities
that don't handle non-text files as gracefully as the coreutils.  But I
definitely agree that it is not something we change lightly.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org