.Dd October 21, 2021
.Dt SERD-FILTER 1
.Os Serd
.Sh NAME
.Nm serd-filter
.Nd print RDF statements that match a pattern
.Sh SYNOPSIS
.Nm serd-filter
.Op Fl hVv
.Op Fl B Ar base
.Op Fl I Ar syntax
.Op Fl O Ar syntax
.Op Fl b Ar bytes
.Op Fl f Ar pattern_file
.Op Fl k Ar bytes
.Op Fl o Ar filename
.Ar pattern
.Op Ar input ...
.Sh DESCRIPTION
.Nm
scans for statements in RDF data.
Its interface is similar to
.Xr grep 1 ,
except patterns are structural:
instead of matching characters within a line,
.Nm
matches nodes within a statement.
.Pp
Data is read from files or standard input,
and only those statements that match the pattern
(or do not match the pattern, if
.Fl v
is given) are written.
By default,
the input syntax is guessed from the file extension,
and line-based output is written to standard output.
.Pp
Patterns are written in NTriples or NQuads with an extension that allows variables like
.Li ?some
or
.Li $thing .
.Pp
The
.Ar input
operands are processed in command-line order.
If
.Ar input
is
.Ar -
or absent,
.Nm
reads from standard input.
.Pp
The options are as follows:
.Pp
.Bl -tag -compact -width 3n
.It Fl B Ar base
Base URI, path, or
.Cm rebase
to use the output path.
See
.Xr serd-pipe 1
for details.
.Pp
.It Fl I Ar syntax
Input syntax or option:
.Cm NQuads ,
.Cm NTriples ,
.Cm TriG ,
.Cm Turtle ,
.Cm lax ,
.Cm variables ,
.Cm relative ,
or
.Cm labels .
See
.Xr serd-pipe 1
for details.
.Pp
.It Fl O Ar syntax
Output syntax or option:
.Cm empty ,
.Cm NQuads ,
.Cm NTriples ,
.Cm TriG ,
.Cm Turtle ,
.Cm ascii ,
.Cm contextual ,
.Cm expanded ,
.Cm verbatim ,
.Cm terse ,
or
.Cm lax .
See
.Xr serd-pipe 1
for details.
.Pp
.It Fl V
Display version information and exit.
.Pp
.It Fl b Ar bytes
I/O block size.
See
.Xr serd-pipe 1
for details.
.Pp
.It Fl f Ar pattern_file
Load pattern from
.Ar pattern_file
instead of the first positional argument.
.Pp
.It Fl h
Print the command line options.
.Pp
.It Fl k Ar bytes
Parser stack size.
See
.Xr serd-pipe 1
for details.
.Pp
.It Fl o Ar filename
Write output to the given
.Ar filename
instead of stdout.
.Pp
.It Fl v
Invert filter to only emit statements that do
.Em not
match the pattern.
.El
.Sh EXIT STATUS
.Nm
exits with a status of 0, or non-zero if an error occured.
.Sh EXAMPLES
To print all type statements:
.Pp
.Dl $ serd-filter '?subject a ?type .' input.ttl
.Pp
To print every statement about http://example.org/subject:
.Pp
.Dl $ serd-filter '<http://example.org/subject> ?p ?o .' input.ttl
.Sh SEE ALSO
.Bl -item -compact
.It
.Xr serd-pipe 1
.It
.Xr serd-sort 1
.It
.Lk http://drobilla.net/software/serd/
.El
.Sh STANDARDS
.Bl -item -compact
.It
.Rs
.%A W3C
.%T RDF 1.1 NQuads
.%D February 2014
.Re
.Lk https://www.w3.org/TR/n-quads/
.It
.Rs
.%A W3C
.%D February 2014
.%T RDF 1.1 NTriples
.Re
.Lk https://www.w3.org/TR/n-triples/
.It
.Rs
.%A W3C
.%T RDF 1.1 TriG
.%D February 2014
.Re
.Lk https://www.w3.org/TR/trig/
.It
.Rs
.%A W3C
.%D February 2014
.%T RDF 1.1 Turtle
.Re
.Lk https://www.w3.org/TR/turtle/
.El
.Sh AUTHORS
.Nm
is a part of serd, by
.An David Robillard
.Mt d@drobilla.net .