Add jpath, a cut(1) that uses JSONPath to describe fields to output.

README

@@ -26,29 +26,54 @@ DESCRIPTION
          {"network":"magnet","channel":"#poe"}
          {"network":"magnet","channel":"#reflex"}
 
+       The jpath filter supports more complex expressions using JSON::Path’s
+       variant of JSONPath.
+
+         % curl −s 'http://api.duckduckgo.com/?q=poe&o=json' |
+         jpath −o '$..Topics.*.FirstURL' −o '$..Topics.*.Text' |
+         grep −i perl |
+         jmap −i col0 −o url −i col1 −o title |
+         json2yaml
+         −−−
+         title: Perl Object Environment, a library for event driven multitasking for the Perl programming language
+         url: http://duckduckgo.com/Perl_Object_Environment
+
 DESIGN GOAL
        Follow the UNIX convention of one record per line of text.  This
        ensures App::PipeFilter tools are compatible with many standard UNIX
-       filters.  In the example above, jcut output is piped through sort(1)
-       and uniq(1) as one might expect.
+       filters.  In the examples above, jcut and jpath output is piped through
+       sort(1), uniq(1) and grep(1).
+
+PRO TIPS
+       JSON isn’t particularly concise, so put grep(1) and other filters that
+       eliminate objects as early as possible in pipelines.
 
 SEE ALSO
        jcut − Extract one or more named fields from JSON input.
 
        jmap − Rename one or more named fields from JSON input.
 
+       jpath − Like jcut, but fields are described using JSON::Path’s variant
+       of JSONPath.
+
        json2yaml − Convert JSON input records to YAML output records.  Some
        people may find YAML output to be more readable.
 
        jsort − Sort JSON input on one or more key fields.
 
        myswl2json − Convert mysql(1) batch output (−B) into JSON records.
 
+       http://json.org/
+
+       http://search.cpan.org/perldoc?JSON::Path
+
+       http://goessner.net/articles/JsonPath/
+
 COPYRIGHT and LICENSE
        App::PipeFilter is Copyright 2011 by Rocco Caputo.  All rights are
        reserved.  App::PipeFilter is released under the same terms as Perl
        itself.
 
 
 
-perl v5.10.0                      2011‐05‐20                App::PipeFilter(3)
+perl v5.10.0                      2011‐05‐21                App::PipeFilter(3)

TODO.otl

@@ -4,6 +4,6 @@
 	[_] 0% Document the libraries.
 	[_] 0% Document the executables.
 	[_] 0% Test dzil.ini.
-[_] % Additional features
-	[_] % Allow -o to be JSON::Path descriptions.
-		This would be easy, except how are the results represented?
+[X] 100% Additional features
+	[X] 100% Allow -o to be JSON::Path descriptions.
+		Implemented jpath that acts like jcut but using JSONPath.

bin/jpath

@@ -0,0 +1,5 @@
+#!/usr/bin/perl
+
+use App::PipeFilter::JsonPath;
+
+App::PipeFilter::JsonPath->new_with_options()->run();

eg/README

@@ -1,6 +1,21 @@
 duckduckgo.json is a sample JSON response from:
-curl 'http://api.duckduckgo.com/?q=poe&o=json' > duckduckgo.json
+curl 'http://api.duckduckgo.com/?q=poe&o=json'
 
-reddit.json is sample JSON from http://www.reddit.com/.json
+reddit.json is sample JSON from:
+curl http://www.reddit.com/.json
 
 sample.json is just some tabular data I put together for testing.
+
+delicious-urlinfo.json comes from:
+curl -s http://feeds.delicious.com/v2/json/urlinfo/7b6cdc20ad985d4ddc547cd18a9e3998
+
+*** Filtering Web Data with JSONPath
+
+% curl -s 'http://api.duckduckgo.com/?q=poe&o=json' |
+jpath -o '$..Topics.*.FirstURL' -o '$..Topics.*.Text' |
+jmap -i col0 -o url -i col1 -o title |
+grep -i perl |
+json2yaml
+--- 
+title: Perl Object Environment, a library for event driven multitasking for the Perl programming language
+url: http://duckduckgo.com/Perl_Object_Environment

eg/delicious-urlinfo.json

@@ -0,0 +1 @@
+[{"hash":"7b6cdc20ad985d4ddc547cd18a9e3998","title":"POE: Perl Object Environment","url":"http:\/\/poe.perl.org\/","total_posts":225,"top_tags":{"perl":204,"programming":104,"poe":100,"framework":73,"development":47,"network":40,"networking":26,"dev":22,"server":16,"software":15}}]

lib/App/PipeFilter.pm

@@ -24,26 +24,52 @@ objects rather than whitespace separated fields.
   {"network":"magnet","channel":"#poe"}
   {"network":"magnet","channel":"#reflex"}
 
+The jpath filter supports more complex expressions using JSON::Path's
+variant of JSONPath.
+
+  % curl -s 'http://api.duckduckgo.com/?q=poe&o=json' |
+  jpath -o '$..Topics.*.FirstURL' -o '$..Topics.*.Text' |
+  grep -i perl |
+  jmap -i col0 -o url -i col1 -o title |
+  json2yaml
+  --- 
+  title: Perl Object Environment, a library for event driven multitasking for the Perl programming language
+  url: http://duckduckgo.com/Perl_Object_Environment
+
 =head1 DESIGN GOAL
 
 Follow the UNIX convention of one record per line of text.  This
 ensures App::PipeFilter tools are compatible with many standard UNIX
-filters.  In the example above, jcut output is piped through sort(1)
-and uniq(1) as one might expect.
+filters.  In the examples above, jcut and jpath output is piped
+through sort(1), uniq(1) and grep(1).
+
+=head1 PRO TIPS
+
+JSON isn't particularly concise, so put grep(1) and other filters that
+eliminate objects as early as possible in pipelines.
 
 =head1 SEE ALSO
 
 jcut - Extract one or more named fields from JSON input.
 
 jmap - Rename one or more named fields from JSON input.
 
+jpath - Like jcut, but fields are described using JSON::Path's
+variant of JSONPath.
+
 json2yaml - Convert JSON input records to YAML output records.  Some
 people may find YAML output to be more readable.
 
 jsort - Sort JSON input on one or more key fields.
 
 myswl2json - Convert mysql(1) batch output (-B) into JSON records.
 
+http://json.org/
+
+http://search.cpan.org/perldoc?JSON::Path
+
+http://goessner.net/articles/JsonPath/
+
 =head1 COPYRIGHT and LICENSE
 
 App::PipeFilter is Copyright 2011 by Rocco Caputo.  All rights are

lib/App/PipeFilter/JsonPath.pm

@@ -0,0 +1,47 @@
+package App::PipeFilter::JsonPath;
+
+use Moose;
+extends 'App::PipeFilter::Generic::Json';
+
+use JSON::Path;
+
+has o => (
+  is            => 'rw',
+  isa           => 'ArrayRef',
+  default       => sub { die "requires one or more -o flag" },
+  lazy          => 1,
+  documentation => 'output fields (a subset of the input)',
+);
+
+has _o => (
+  is            => 'rw',
+  isa           => 'ArrayRef[JSON::Path]',
+  lazy          => 1,
+  default       => sub {
+		my $self = shift;
+		return [ map { JSON::Path->new($_) } @{$self->o()} ];
+	},
+);
+
+sub transform {
+  my $self = shift();
+
+  my @json_paths = @{$self->_o()};
+
+  my @output;
+
+  my $c = 0;
+  foreach my $json_path (@json_paths) {
+    my $r = 0;
+    foreach my $json_value ($json_path->values($_[0])) {
+      $output[$r++]{"col$c"} = $json_value;
+    }
+    ++$c;
+  }
+
+	return @output;
+}
+
+1;
+
+# vim: ts=2 sw=2 expandtab