[Bug 1621226] Re: grep does not output null when -o -z is used

[Robie Basak]

<jarnos> rbasak, well, that bug has not got any visible attention from
others, so I don't know who I am discussing it with.

<jarnos> rbasak, no-one should rely on behavior that makes output
ambiguous. The bug is fixed in 16.04 anyway.

<rbasak> jarnos: I don't think it matters where users "should" rely on
behaviour or not. For a stable release, what matters is if they *are*,
and if an SRU will break them.

<jarnos> rbasak, their scripts are broken anyway.

<rbasak> jarnos: it doesn't matter. If their scripts happen to work now,
and we change behaviour in an SRU such that they break, then that needs
to be considered.

<rbasak> jarnos: unless you can demonstrate that it isn't possible to
write a script that would change behaviour after your proposed update?

<rbasak> jarnos: you'd be discussing the issue with me in the bug, but
also leaving a record of the discussion so that if another member of the
SRU team considers the bug, that person can see the previous discussion.

<rbasak> jarnos: presumably you need the fix for some reason. But there
are other ways to find a workaround that don't involve changing
behaviour but might be useful to affected users. For example, a flag in
the environment. These should be discussed, but I feel you first need to
understand my point about not breaking users despite their scripts
"being broken".

<rbasak> You can't dismiss users like that.

<rbasak> Just because they're wrong doesn't mean we can break them in a
stable release.

<jarnos> rbasak, how would a flag in environment help?

<jarnos> rbasak, fixing the bug would make it possible for them to fix
their scripts.

<rbasak> jarnos: you could land an SRU that doesn't change behaviour,
except when you want it to do so.

<rbasak> jarnos: 16.04 makes it possible for them to fix their scripts.

<rbasak> jarnos: and an environment flag would also do this for 14.04,
but without breaking users surprisingly.

<jarnos> rbasak, not, if you want to make a script that works in both.

<rbasak> jarnos: if you want a script that works in both, SRU my
environment flag proposal, then set the environment in your script.
You'll then get consistent behaviour in both. I'm not saying it has to
be this way, but it is an option that minimises regression risk to
existing users.

<jarnos> rbasak,  What is your environment flag proposal?

<rbasak> jarnos: SRU the fix to 14.04, but adjust it so that it
maintains previous broken behaviour unless the environment variable
FIX_LP_1621226 is set.

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https://bugs.launchpad.net/bugs/1621226

Title:
  grep does not output null when -o -z is used

Status in grep package in Ubuntu:
  Fix Released
Status in grep source package in Trusty:
  New

Bug description:
  Impact

  Grepping null terminated records with -o option does not work. There
  may be a newline in a matched string, so the output may be ambiguous
  as the matched parts are separated by newline. This bug prevents users
  from using grep in some scripts that they want to work in all
  supported releases.

  Test Case

  $ printf 'a\0b\0b1' | grep --null-data b | hexdump -C
  00000000  62 00 62 31 00                                    |b.b1.|
  00000005

  but

  $ printf 'a\0b\0b1' | grep -o --null-data b | hexdump -C
  00000000  62 0a 62 0a                                       |b.b.|
  00000004

  Expected result:
  00000000  62 00 62 00                                       |b.b.|
  00000004

  Regression Potential

  Not remarkable. Scripts using -o -z are broken anyway with the broken
  grep.

  This is fixed in Xenial, but IMO should be fixed in Trusty, too.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: grep 2.16-1
  ProcVersionSignature: Ubuntu 4.4.0-37.56~14.04.1-generic 4.4.19
  Uname: Linux 4.4.0-37-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.21
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Wed Sep  7 22:48:42 2016
  EcryptfsInUse: Yes
  InstallationDate: Installed on 2014-09-21 (717 days ago)
  InstallationMedia: Ubuntu-Studio 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.1)
  SourcePackage: grep
  UpgradeStatus: No upgrade log present (probably fresh install)

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