I upgraded grep from version 3.7-1 to 3.8-1. Something in the readme
says that "Upstream has made egrep and fgrep obsolecent."

Now chkrootkit spews a bunch of relatively harmless warnings:

egrep: warning: egrep is obsolescent; using grep -E

There is discussion of the egrep messages at
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1019335 and it looks
like a new grep will be uploaded next week that will stop these
messages appearing, so these will go away. You can also use the
various mechanisms to filter the output to remove the messages. (See
README.Debian and the various links therein)

In the longer term chkrootkit should probably be patched to replace
calls to egrep with 'grep -E' - however, this is slightly more
involved than you might guess given the calls to egrep are indirect
(using $egrep variable, which is itself set from TROJAN variable -
there may be some other issues with how this is done); and ideally
$egrep would continue to honour the '-p' setting after any change.

(Also chkrootkit is considering egrep as potentially a binary that
should be scanned for issues - if TROJAN is changed then there also
needs to be a change to ensure the chk_egrep test is still attempted.
But it also looks a little strange that  chk_grep is looking for a
different thing  to chk_egrep. suggest they should be combined)

We believe that the bug you reported is fixed in the latest version of
chkrootkit, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1019460@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Richard Lewis <richard.lewis.debian@googlemail.com> (supplier of updated chkrootkit package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sun, 12 Mar 2023 12:31:00 +0100
Source: chkrootkit
Architecture: source
Version: 0.57-2
Distribution: unstable
Urgency: medium
Maintainer: Debian Security Tools <team+pkg-security@tracker.debian.org>
Changed-By: Richard Lewis <richard.lewis.debian@googlemail.com>
Closes: 589682 745433 1019460 1032122
Changes:
 chkrootkit (0.57-2) unstable; urgency=medium
 .
   [ Richard Lewis ]
   * Team upload
   * Fix several tests that did not work, contained syntax errors or
      where the output did not make clear what had been found
      (and remove spurious file in /usr/lib/chkrootkit/1 created as a result,
      thanks to Thomas Dorner)
      (Closes: #1032122, #589682)
   * Update autopkgtests to avoid warnings from grep (Thanks to Seb35)
      (Closes: #1019460)
   * Add systemd timer (Closes: #745433 as you can change the time the unit runs)
   * Add NEWS.Debian to document disabled tests
   * All lintian warnings are now fixed or overridden
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