Date: Mon, 12 Jan 2015 16:52:41 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: freebsd-questions@freebsd.org Subject: Re: pkg-info: supplying word boundary in regex Message-ID: <54B3FBD9.8090009@infracaninophile.co.uk> In-Reply-To: <20150112154038.GA41662@holstein.holy.cow> References: <20150112154038.GA41662@holstein.holy.cow>
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On 2015/01/12 15:40, parv@pair.com wrote:
> (Running pkg 1.4.4 on FreeBSD 8-STABLE here.)
>=20
> Could somebody tell me please the syntax for word boundary in regex
> for pkg-info ...
>=20
> pkg info -x '...'
>=20
>=20
> ... ?
>=20
> The pkg-info manual page says ...
>=20
> -x, --regex
> Treat pkg-name as a regular expression according to the "modern"
> or "extended" syntax of re_format(7).
>=20
> ... and re_format man page says ...
>=20
> There are two special cases=3D of bracket expressions: the bracket
> expressions `[[:<:]]' and `[[:>:]]' match the null string at the
> beginning and end of a word respectively. A word is defined as a
> sequence of word characters which is neither preceded nor followed
> by word characters. A word character is an alnum character (as
> defined by ctype(3)) or an underscore.
>=20
> ... then specifying a word boundary as "x[[:>:]]" (to match "x" at the
> end of a "word") causes "Invalid regex" error. For example, to get
> result only for "tex" (avoiding packages with "text" as string in a
> package name[0]) ...
>=20
> # pkg info -x 'tex[[:>:]]'
> pkg: sqlite error while executing iterator in file \
> pkgdb_iterator.c:905: Invalid regex
Normally I'd suggest trying:
# env DEBUG=3D4 pkg info -x 'tex[[:>:]]'
which should display exactly what SQL is being run. However it appears
that the error occurs before Sqlite does any querying -- it must be
while compiling the RE.
>=20
> Does pkg overstate its support for re_format(7) then?
>=20
>=20
> - parv
>=20
>=20
> [0] Yes, I realize if a name happens to be "text-tex" I would also
> get a result & that would be expected. Common case is that
> packages here have only either "text" or "tex" exclusively in
> the name.
>=20
There is always "pkg info -x 'tex$' to anchor the RE at the end of a
string. However that doesn't really answer your question.
The re_format(7) support comes straight out of libc -- it's compiled as
a loadable module for sqlite, so that queries of the form:
SELECT foo FROM bar WHERE foo REXEP 'some-re' ;
should be using re_format(7) style REGEXPs. Admittedly, we haven't
tested all the odd corner cases for regular expression syntax. Cn you
raise an issue on github please?
Cheers,
Matthew
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