Date: Sat, 2 Nov 2019 13:45:05 +0700 From: Victor Sudakov <vas@sibptus.ru> To: freebsd-questions@freebsd.org Subject: Re: grep for ascii nul Message-ID: <20191102064505.GA98558@admin.sibptus.ru> In-Reply-To: <63808.1572638827@segfault.tristatelogic.com> References: <20191101092716.GA67658@admin.sibptus.ru> <63808.1572638827@segfault.tristatelogic.com>
next in thread | previous in thread | raw e-mail | index | archive | help
--/04w6evG8XlLl3ft
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
Ronald F. Guilmette wrote:
> In message <20191101092716.GA67658@admin.sibptus.ru>,=20
> Victor Sudakov <vas@sibptus.ru> wrote:
>=20
> >I need to find files containing ascii null inside, and print their names=
to
> > stdout.
>=20
> Unfortunately, you're banging up against a long-standing a rather
> annoying non-feature of fgrep/grep/egrep, which is that unlike the
> tr command, the grep family of commands does not support the \DDD
> notation for specifying arbitrary byte values. Thus, you cannot use
> then to search for arbitrary byte values.
>=20
> I would thus suggest that you solve your problem using a Perl or C
> program. =20
Perl is not in the base system, so that is not quite the answer.=20
I'm a big fan of awk, awk is in the base system and should be able to do
it, right?
$ hd trees.txt=20
00000000 66 69 72 0a 6f 61 6b 0a 63 65 64 00 61 72 0a 62 |fir.oak.ced.ar=
=2Eb|
00000010 69 72 63 68 0a 70 61 6c 6d 0a |irch.palm.|
0000001a
$=20
Note the ascii null embedded in the word "cedar"
$ awk '/\x66\x69/{print $0}' trees.txt
fir
So far so good. But with the ascii nul it behaves in an unexpected way:
$ awk '/\x00/{print $0}' trees.txt
fir
oak
ced
birch
palm
$=20
--=20
Victor Sudakov, VAS4-RIPE, VAS47-RIPN
2:5005/49@fidonet http://vas.tomsk.ru/
--/04w6evG8XlLl3ft
Content-Type: application/pgp-signature; name="signature.asc"
-----BEGIN PGP SIGNATURE-----
iQEcBAEBAgAGBQJdvSXxAAoJEA2k8lmbXsY0qWwH/RkTNDcpCPx62KmkBx99CG6V
NiohEjWgP0ZNpna6EKwHLKhO6ZV+zi9rBJbTS9u/Rwx8oH9NQnCVbhhHV9s5bzjq
hnwajl7WeAp6b2KpfG1kMoVS68vUUJ/sSIa5VFmVX/gBu+6e+RqRHsM21IoW/UJA
hqgr5sPCL/9nYo7EeMi0UkZxsnkYQXGcvsSCGk6Cabk15eA669A1qdqzlz/LBBdp
oJdAHOFrlKaO1xrHaUFRJlCIUmbe8ObhY1UY0hPFCRThlExvVOl2L4A6ei/Nfatj
DXW9sVLHuMR922CbIE1pzeQQt7d1iJKZbqzOCFrRA21Ko7EdLV6+eGEgrSP3AHA=
=afP5
-----END PGP SIGNATURE-----
--/04w6evG8XlLl3ft--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20191102064505.GA98558>