From 65844244e2fdf9a839a5bc6c0010822b4435c4e2 Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 17:15:35 -0700
Subject: [PATCH 01/10] json mode

---
 Readme.md        | 16 ++++++++++++++++
 bin/pru          | 22 +++++++++++++++++++++-
 lib/pru.rb       | 42 ++++++++++++++++++++++++++++++++++++++++++
 spec/pru_spec.rb | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/Readme.md b/Readme.md
index 9215143..5ab857f 100644
--- a/Readme.md
+++ b/Readme.md
@@ -32,6 +32,21 @@ Pipeable Ruby - forget about grep / sed / awk / wc ... use pure, readable Ruby!
     # select lines longer than 5 letters, then join with commas
     ls -1 | pru 'size > 5' 'join(",")'
     
+## JSON - each parsed value
+
+Parse a stream of JSON values (newline-delimited or pretty-printed multiline)
+into items. Hash/Array results are pretty-printed, everything else is printed
+plainly so it pipes nicely into other tools.
+
+    # pull a field out of each object
+    printf '{"a":1}\n{"a":2}\n' | pru --json 'self["a"]'
+
+    # filter objects
+    printf '{"n":1}\n{"n":5}\n' | pru --json 'self["n"] > 3'
+
+    # map then reduce
+    printf '{"a":1}\n{"a":2}\n' | pru --json 'self["a"]' 'sum'
+
 ## Inplace edit
 
     pru -i Gemfile 'sub /ruby/, "foo"'
@@ -51,6 +66,7 @@ curl https://rubinjam.herokuapp.com/pack/pru > pru && chmod +x pru
 ## Options
 
     -r, --reduce CODE                reduce via CODE
+    -j, --json                       Parse input as a JSON stream, each value is an item
 
     -I, --libdir DIR                 Add DIR to load path
         --require LIB                Require LIB (also comma-separated)
diff --git a/bin/pru b/bin/pru
index ecaf4de..2ee8655 100755
--- a/bin/pru
+++ b/bin/pru
@@ -28,6 +28,7 @@ OptionParser.new do |opts|
     Options:
   BANNER
   opts.on("-r", "--reduce CODE","reduce via CODE") {|code| options[:reduce] = code }
+  opts.on("-j", "--json","Parse input as a JSON stream, each value is an item") { options[:json] = true }
   opts.separator ''
   opts.on('-I', '--libdir DIR', 'Add DIR to load path') { |dir| $LOAD_PATH << dir }
   opts.on('--require LIB', 'Require LIB (also comma-separated)') { |lib| lib.split(',').each{|l| require l } }
@@ -58,7 +59,18 @@ else
   input = $stdin
 end
 
+if options[:json]
+  require 'json'
+  format = lambda do |out|
+    case out
+    when Hash, Array then JSON.pretty_generate(out)
+    else out
+    end
+  end
+end
+
 collector = lambda do |line|
+  line = format.call(line) if format
   if output_lines
     output_lines << line
   else
@@ -70,7 +82,15 @@ collector = lambda do |line|
   end
 end
 
-if reduce
+if options[:json]
+  if reduce
+    results = []
+    Pru.json_map(input, map) { |out| results << out }
+    collector.call Pru.json_reduce(results, reduce)
+  else
+    Pru.json_map(input, map) { |out| collector.call out }
+  end
+elsif reduce
   results = []
   Pru.map(input, map) { |out| results << out }
   collector.call Pru.reduce(results, reduce)
diff --git a/lib/pru.rb b/lib/pru.rb
index 50c2022..fbdf029 100644
--- a/lib/pru.rb
+++ b/lib/pru.rb
@@ -31,5 +31,47 @@ def _pru
       RUBY
       array._pru
     end
+
+    def json_map(io, code)
+      block = compile(code)
+      i = 0
+      each_json(io) do |item|
+        i += 1
+        result = item.instance_exec(i, &block) or next
+
+        case result
+        when true then yield item
+        else yield result
+        end
+      end
+    end
+
+    def json_reduce(array, code)
+      array.instance_exec(&compile(code))
+    end
+
+    private
+
+    def compile(code)
+      eval("proc { |i| #{code} }", TOPLEVEL_BINDING, __FILE__, __LINE__)
+    end
+
+    # Parse a stream of concatenated JSON values (newline-delimited or multiline)
+    # by accumulating lines until the buffer forms a complete value.
+    def each_json(io)
+      require 'json'
+      buffer = +""
+      io.each_line do |line|
+        buffer << line
+        begin
+          item = JSON.parse(buffer)
+        rescue JSON::ParserError
+          next
+        end
+        yield item
+        buffer = +""
+      end
+      raise JSON::ParserError, "unexpected trailing input: #{buffer.strip}" unless buffer.strip.empty?
+    end
   end
 end
diff --git a/spec/pru_spec.rb b/spec/pru_spec.rb
index cf34188..4ed24a6 100644
--- a/spec/pru_spec.rb
+++ b/spec/pru_spec.rb
@@ -112,6 +112,40 @@
     end
   end
 
+  describe '--json' do
+    it "pretty-prints hashes" do
+      `printf '{"a":1}\n' | ./bin/pru --json`.should == "{\n  \"a\": 1\n}\n"
+    end
+
+    it "parses multiple values from one line" do
+      `printf '{"a":1}\n{"b":2}\n' | ./bin/pru --json 'keys.first'`.should == "a\nb\n"
+    end
+
+    it "parses values spanning multiple lines" do
+      `printf '{\n  "a": 1\n}\n' | ./bin/pru --json 'self["a"]'`.should == "1\n"
+    end
+
+    it "outputs strings plainly without quotes" do
+      `printf '{"a":"foo"}\n' | ./bin/pru --json 'self["a"]'`.should == "foo\n"
+    end
+
+    it "outputs numbers plainly" do
+      `printf '{"a":1}\n{"a":2}\n' | ./bin/pru --json 'self["a"]'`.should == "1\n2\n"
+    end
+
+    it "selects via true" do
+      `printf '{"n":1}\n{"n":5}\n' | ./bin/pru --json 'self["n"] > 3'`.should == "{\n  \"n\": 5\n}\n"
+    end
+
+    it "reduces" do
+      `printf '{"a":1}\n{"a":2}\n' | ./bin/pru --json 'self["a"]' 'sum'`.should == "3\n"
+    end
+
+    it "pretty-prints array reduce results" do
+      `printf '{"a":1}\n{"a":2}\n' | ./bin/pru --json '' 'map { |h| h["a"] }'`.should == "[\n  1,\n  2\n]\n"
+    end
+  end
+
   describe '-I / --libdir' do
     it "adds a folder to the load-path" do
       `echo 1 | ./bin/pru -I spec --reduce 'require "a_test"; ATest.to_s'`.should == "ATest\n"

From e2e382f214645f5184be2565ab6b881ca3dc54a5 Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 17:20:21 -0700
Subject: [PATCH 02/10] k8s

---
 Readme.md        |  9 +++++++++
 bin/pru          |  5 +++--
 lib/pru.rb       | 18 ++++++++++++++++--
 spec/pru_spec.rb | 14 ++++++++++++++
 4 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/Readme.md b/Readme.md
index 5ab857f..b1f9526 100644
--- a/Readme.md
+++ b/Readme.md
@@ -47,6 +47,14 @@ plainly so it pipes nicely into other tools.
     # map then reduce
     printf '{"a":1}\n{"a":2}\n' | pru --json 'self["a"]' 'sum'
 
+## Kubernetes - each item
+
+Like `--json`, but if the first value has an `"items"` key (as `kubectl ... -o json`
+returns) its elements are iterated instead.
+
+    # list pod names
+    kubectl get pods -A -o json | pru --k8s 'dig("metadata", "name")'
+
 ## Inplace edit
 
     pru -i Gemfile 'sub /ruby/, "foo"'
@@ -67,6 +75,7 @@ curl https://rubinjam.herokuapp.com/pack/pru > pru && chmod +x pru
 
     -r, --reduce CODE                reduce via CODE
     -j, --json                       Parse input as a JSON stream, each value is an item
+    -k, --k8s                        Like --json, but iterate the "items" array if present (kubectl -o json)
 
     -I, --libdir DIR                 Add DIR to load path
         --require LIB                Require LIB (also comma-separated)
diff --git a/bin/pru b/bin/pru
index 2ee8655..433b945 100755
--- a/bin/pru
+++ b/bin/pru
@@ -29,6 +29,7 @@ OptionParser.new do |opts|
   BANNER
   opts.on("-r", "--reduce CODE","reduce via CODE") {|code| options[:reduce] = code }
   opts.on("-j", "--json","Parse input as a JSON stream, each value is an item") { options[:json] = true }
+  opts.on("-k", "--k8s","Like --json, but iterate the \"items\" array if present (kubectl -o json)") { options[:json] = true; options[:k8s] = true }
   opts.separator ''
   opts.on('-I', '--libdir DIR', 'Add DIR to load path') { |dir| $LOAD_PATH << dir }
   opts.on('--require LIB', 'Require LIB (also comma-separated)') { |lib| lib.split(',').each{|l| require l } }
@@ -85,10 +86,10 @@ end
 if options[:json]
   if reduce
     results = []
-    Pru.json_map(input, map) { |out| results << out }
+    Pru.json_map(input, map, k8s: options[:k8s]) { |out| results << out }
     collector.call Pru.json_reduce(results, reduce)
   else
-    Pru.json_map(input, map) { |out| collector.call out }
+    Pru.json_map(input, map, k8s: options[:k8s]) { |out| collector.call out }
   end
 elsif reduce
   results = []
diff --git a/lib/pru.rb b/lib/pru.rb
index fbdf029..300425c 100644
--- a/lib/pru.rb
+++ b/lib/pru.rb
@@ -32,10 +32,10 @@ def _pru
       array._pru
     end
 
-    def json_map(io, code)
+    def json_map(io, code, k8s: false)
       block = compile(code)
       i = 0
-      each_json(io) do |item|
+      each_item(io, k8s) do |item|
         i += 1
         result = item.instance_exec(i, &block) or next
 
@@ -56,6 +56,20 @@ def compile(code)
       eval("proc { |i| #{code} }", TOPLEVEL_BINDING, __FILE__, __LINE__)
     end
 
+    # Yield items from a JSON stream. In k8s mode, if the first value has an
+    # "items" key (e.g. `kubectl get ... -o json`) its elements are yielded instead.
+    def each_item(io, k8s)
+      first = true
+      each_json(io) do |item|
+        if k8s && first && item.is_a?(Hash) && item.key?("items")
+          item.fetch("items").each { |i| yield i }
+        else
+          yield item
+        end
+        first = false
+      end
+    end
+
     # Parse a stream of concatenated JSON values (newline-delimited or multiline)
     # by accumulating lines until the buffer forms a complete value.
     def each_json(io)
diff --git a/spec/pru_spec.rb b/spec/pru_spec.rb
index 4ed24a6..11b9f82 100644
--- a/spec/pru_spec.rb
+++ b/spec/pru_spec.rb
@@ -146,6 +146,20 @@
     end
   end
 
+  describe '--k8s' do
+    it "iterates the items array" do
+      `printf '{"items":[{"metadata":{"name":"a"}},{"metadata":{"name":"b"}}]}\n' | ./bin/pru --k8s 'dig("metadata", "name")'`.should == "a\nb\n"
+    end
+
+    it "behaves like --json when there is no items key" do
+      `printf '{"metadata":{"name":"solo"}}\n' | ./bin/pru --k8s 'dig("metadata", "name")'`.should == "solo\n"
+    end
+
+    it "reduces over the items" do
+      `printf '{"items":[{"metadata":{"name":"a"}},{"metadata":{"name":"b"}}]}\n' | ./bin/pru --k8s 'dig("metadata", "name")' 'size'`.should == "2\n"
+    end
+  end
+
   describe '-I / --libdir' do
     it "adds a folder to the load-path" do
       `echo 1 | ./bin/pru -I spec --reduce 'require "a_test"; ATest.to_s'`.should == "ATest\n"

From b496f99f1291ef4ae4a597f0c12b548188ff3f74 Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 17:22:07 -0700
Subject: [PATCH 03/10] simplify usage

---
 bin/pru | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/bin/pru b/bin/pru
index 433b945..8d4c29d 100755
--- a/bin/pru
+++ b/bin/pru
@@ -7,10 +7,9 @@ $LOAD_PATH << "#{root}/lib" if File.exist?("#{root}/Gemfile")
 
 require 'pru'
 
-usage = nil
 options = {}
 
-OptionParser.new do |opts|
+parser = OptionParser.new do |opts|
   opts.banner = <<-BANNER.gsub(/^    /, "")
     Pipeable Ruby
 
@@ -37,15 +36,19 @@ OptionParser.new do |opts|
   opts.separator ''
   opts.on("-h", "--help","Show this.") { puts opts; exit }
   opts.on('-v', '--version','Show Version'){ require 'pru/version'; puts Pru::VERSION; exit}
-  usage = opts
-end.parse!
+end
+parser.parse!
 
-if ARGV.empty? && options.empty? # no arguments -> show usage
-  puts usage
+# no arguments -> show usage
+if ARGV.empty? && options.empty?
+  puts parser
   exit
 end
 
-abort "Too many arguments, see --help" if ARGV.size > 2
+# bad arguments -> fail
+if ARGV.size > 2
+  abort "Too many arguments, see --help"
+end
 
 map, reduce = ARGV
 reduce ||= options[:reduce]

From ef73276cddf1ceae4d5f926505ce4be18fbf033b Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 17:28:36 -0700
Subject: [PATCH 04/10] usage

---
 bin/pru          |  8 +++++---
 spec/pru_spec.rb | 10 ++++++++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/bin/pru b/bin/pru
index 8d4c29d..60b7301 100755
--- a/bin/pru
+++ b/bin/pru
@@ -39,16 +39,18 @@ parser = OptionParser.new do |opts|
 end
 parser.parse!
 
-# no arguments -> show usage
+# no arguments -> show usage and fail
 if ARGV.empty? && options.empty?
-  puts parser
-  exit
+  abort parser.to_s
 end
 
 # bad arguments -> fail
 if ARGV.size > 2
   abort "Too many arguments, see --help"
 end
+if ARGV.size == 2 && options[:reduce]
+  abort "Cannot combine a reduce argument with --reduce, see --help"
+end
 
 map, reduce = ARGV
 reduce ||= options[:reduce]
diff --git a/spec/pru_spec.rb b/spec/pru_spec.rb
index 11b9f82..355daa8 100644
--- a/spec/pru_spec.rb
+++ b/spec/pru_spec.rb
@@ -6,8 +6,9 @@
     Pru::VERSION.should =~ /^\d+\.\d+\.\d+$/
   end
 
-  it "shows help when no arguments are given" do
-    `./bin/pru`.should include('Usage:')
+  it "shows usage and fails when no arguments are given" do
+    `./bin/pru 2>&1`.should include('Usage:')
+    $?.success?.should == false
   end
 
   it 'shows -v' do
@@ -110,6 +111,11 @@
     it "selects with empty string and reduces" do
       `cat spec/test.txt | ./bin/pru '' 'size'`.should == "5\n"
     end
+
+    it "fails when combining a reduce argument with --reduce" do
+      `echo x | ./bin/pru self size --reduce size 2>&1`.should include("Cannot combine a reduce argument with --reduce")
+      $?.success?.should == false
+    end
   end
 
   describe '--json' do

From cdd3525cc82cdf689fa500adf782f335e990ce5f Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 17:32:35 -0700
Subject: [PATCH 05/10] inplace vs no code

---
 bin/pru          |  7 ++++---
 spec/pru_spec.rb | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/bin/pru b/bin/pru
index 60b7301..4db2137 100755
--- a/bin/pru
+++ b/bin/pru
@@ -39,18 +39,19 @@ parser = OptionParser.new do |opts|
 end
 parser.parse!
 
-# no arguments -> show usage and fail
+# bad arguments -> fail
 if ARGV.empty? && options.empty?
   abort parser.to_s
 end
-
-# bad arguments -> fail
 if ARGV.size > 2
   abort "Too many arguments, see --help"
 end
 if ARGV.size == 2 && options[:reduce]
   abort "Cannot combine a reduce argument with --reduce, see --help"
 end
+if options[:file] && ARGV.empty? && !options[:reduce]
+  abort "No code given for --inplace-edit, see --help"
+end
 
 map, reduce = ARGV
 reduce ||= options[:reduce]
diff --git a/spec/pru_spec.rb b/spec/pru_spec.rb
index 355daa8..25260b3 100644
--- a/spec/pru_spec.rb
+++ b/spec/pru_spec.rb
@@ -150,6 +150,15 @@
     it "pretty-prints array reduce results" do
       `printf '{"a":1}\n{"a":2}\n' | ./bin/pru --json '' 'map { |h| h["a"] }'`.should == "[\n  1,\n  2\n]\n"
     end
+
+    it "works with inplace-edit" do
+      Tempfile.create do |f|
+        f.write "{\"a\":1}\n{\"a\":2}\n"
+        f.close
+        `./bin/pru --inplace-edit #{f.path} --json 'self["a"]'`.should == ''
+        File.read(f.path).should == "1\n2\n"
+      end
+    end
   end
 
   describe '--k8s' do
@@ -197,6 +206,11 @@
       `./bin/pru --inplace-edit xxx size 2>&1`.sub(' @ rb_sysopen', '').should include('No such file or directory - xxx')
     end
 
+    it "fails when no code is given" do
+      `./bin/pru --inplace-edit xxx 2>&1`.should include('No code given for --inplace-edit')
+      $?.success?.should == false
+    end
+
     it "keeps line separators when modifying" do
       File.open('xxx','w'){|f| f.write "abc\r\nab\r\na" }
       `./bin/pru --inplace-edit xxx size`.should == ''

From d853d9d25abdf9ea370fad3ef5806fec1e04319b Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 17:40:06 -0700
Subject: [PATCH 06/10] styl

---
 bin/pru | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/bin/pru b/bin/pru
index 4db2137..a46aa4b 100755
--- a/bin/pru
+++ b/bin/pru
@@ -61,14 +61,15 @@ if options[:file]
   output_lines = []
   input = File.read(options[:file])
   newline = input[/\r\n|\r|\n/]
-  trailing_newline = (input =~ /#{newline}\Z/)
+  trailing_newline = (newline && input.end_with?(newline))
 else
   input = $stdin
 end
 
+# dump write as JSON ?
 if options[:json]
   require 'json'
-  format = lambda do |out|
+  output_format = lambda do |out|
     case out
     when Hash, Array then JSON.pretty_generate(out)
     else out
@@ -77,7 +78,7 @@ if options[:json]
 end
 
 collector = lambda do |line|
-  line = format.call(line) if format
+  line = output_format.call(line) if output_format
   if output_lines
     output_lines << line
   else

From 747ef186a1b41ca1c2aba938c8a224781977b1d0 Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 18:24:40 -0700
Subject: [PATCH 07/10] unify

---
 bin/pru    | 20 +++++++++-----------
 lib/pru.rb | 54 +++++++++++++-----------------------------------------
 2 files changed, 22 insertions(+), 52 deletions(-)

diff --git a/bin/pru b/bin/pru
index a46aa4b..3b1b331 100755
--- a/bin/pru
+++ b/bin/pru
@@ -90,20 +90,18 @@ collector = lambda do |line|
   end
 end
 
-if options[:json]
-  if reduce
-    results = []
-    Pru.json_map(input, map, k8s: options[:k8s]) { |out| results << out }
-    collector.call Pru.json_reduce(results, reduce)
-  else
-    Pru.json_map(input, map, k8s: options[:k8s]) { |out| collector.call out }
-  end
-elsif reduce
+items = if options[:json]
+  Pru.each_json_item(input, k8s: options[:k8s])
+else
+  input.each_line.lazy.map { |line| line.chomp }
+end
+
+if reduce
   results = []
-  Pru.map(input, map) { |out| results << out }
+  Pru.map(items, map) { |out| results << out }
   collector.call Pru.reduce(results, reduce)
 else
-  Pru.map(input, map) { |out| collector.call out }
+  Pru.map(items, map) { |out| collector.call out }
 end
 
 if options[:file]
diff --git a/lib/pru.rb b/lib/pru.rb
index 300425c..2d0f618 100644
--- a/lib/pru.rb
+++ b/lib/pru.rb
@@ -2,63 +2,29 @@
 
 module Pru
   class << self
-    def map(io, code)
-      String.class_eval <<-RUBY, __FILE__, __LINE__ + 1
-        def _pru(i)
-          #{code}
-        end
-      RUBY
-
-      i = 0
-      io.each_line do |line|
-        i += 1
-        line.chomp!
-        result = line._pru(i) or next
-
-        case result
-        when true then yield line
-        when Regexp then yield line if line =~ result
-        else yield result
-        end
-      end
-    end
-
-    def reduce(array, code)
-      Array.class_eval <<-RUBY, __FILE__, __LINE__ + 1
-        def _pru
-          #{code}
-        end
-      RUBY
-      array._pru
-    end
-
-    def json_map(io, code, k8s: false)
+    def map(items, code)
       block = compile(code)
       i = 0
-      each_item(io, k8s) do |item|
+      items.each do |item|
         i += 1
-        result = item.instance_exec(i, &block) or next
+        result = item.instance_exec(i, &block) || next
 
         case result
         when true then yield item
+        when Regexp then yield item if item =~ result
         else yield result
         end
       end
     end
 
-    def json_reduce(array, code)
+    def reduce(array, code)
       array.instance_exec(&compile(code))
     end
 
-    private
-
-    def compile(code)
-      eval("proc { |i| #{code} }", TOPLEVEL_BINDING, __FILE__, __LINE__)
-    end
-
     # Yield items from a JSON stream. In k8s mode, if the first value has an
     # "items" key (e.g. `kubectl get ... -o json`) its elements are yielded instead.
-    def each_item(io, k8s)
+    def each_json_item(io, k8s: false)
+      return enum_for(:each_json_item, io, k8s: k8s) unless block_given?
       first = true
       each_json(io) do |item|
         if k8s && first && item.is_a?(Hash) && item.key?("items")
@@ -70,6 +36,12 @@ def each_item(io, k8s)
       end
     end
 
+    private
+
+    def compile(code)
+      eval("proc { |i| #{code} }", TOPLEVEL_BINDING, __FILE__, __LINE__)
+    end
+
     # Parse a stream of concatenated JSON values (newline-delimited or multiline)
     # by accumulating lines until the buffer forms a complete value.
     def each_json(io)

From b351508190039cd3a0cdc8982eb5e6d241adc1e6 Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 18:28:26 -0700
Subject: [PATCH 08/10] first

---
 Readme.md  | 2 +-
 lib/pru.rb | 8 +++-----
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/Readme.md b/Readme.md
index b1f9526..f09eda4 100644
--- a/Readme.md
+++ b/Readme.md
@@ -49,7 +49,7 @@ plainly so it pipes nicely into other tools.
 
 ## Kubernetes - each item
 
-Like `--json`, but if the first value has an `"items"` key (as `kubectl ... -o json`
+Like `--json`, but if the value has an `"items"` key (as `kubectl ... -o json`
 returns) its elements are iterated instead.
 
     # list pod names
diff --git a/lib/pru.rb b/lib/pru.rb
index 2d0f618..2382f5a 100644
--- a/lib/pru.rb
+++ b/lib/pru.rb
@@ -21,18 +21,16 @@ def reduce(array, code)
       array.instance_exec(&compile(code))
     end
 
-    # Yield items from a JSON stream. In k8s mode, if the first value has an
+    # Yield items from a JSON stream. In k8s mode, if the value has an
     # "items" key (e.g. `kubectl get ... -o json`) its elements are yielded instead.
     def each_json_item(io, k8s: false)
       return enum_for(:each_json_item, io, k8s: k8s) unless block_given?
-      first = true
       each_json(io) do |item|
-        if k8s && first && item.is_a?(Hash) && item.key?("items")
+        if k8s && item.is_a?(Hash) && item.key?("items")
           item.fetch("items").each { |i| yield i }
         else
           yield item
         end
-        first = false
       end
     end
 
@@ -44,8 +42,8 @@ def compile(code)
 
     # Parse a stream of concatenated JSON values (newline-delimited or multiline)
     # by accumulating lines until the buffer forms a complete value.
+    # TODO: this is not very efficient, but keeping track of opening/closing braces might be ugly too
     def each_json(io)
-      require 'json'
       buffer = +""
       io.each_line do |line|
         buffer << line

From a9a7fcfc57c2135b49eada107131c84c18d67f1e Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 18:35:44 -0700
Subject: [PATCH 09/10] clean

---
 bin/pru    |  2 +-
 lib/pru.rb | 19 ++++++++++---------
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/bin/pru b/bin/pru
index 3b1b331..9a03502 100755
--- a/bin/pru
+++ b/bin/pru
@@ -91,7 +91,7 @@ collector = lambda do |line|
 end
 
 items = if options[:json]
-  Pru.each_json_item(input, k8s: options[:k8s])
+  Pru.json_items(input, k8s: options[:k8s])
 else
   input.each_line.lazy.map { |line| line.chomp }
 end
diff --git a/lib/pru.rb b/lib/pru.rb
index 2382f5a..69d6b7e 100644
--- a/lib/pru.rb
+++ b/lib/pru.rb
@@ -21,15 +21,16 @@ def reduce(array, code)
       array.instance_exec(&compile(code))
     end
 
-    # Yield items from a JSON stream. In k8s mode, if the value has an
-    # "items" key (e.g. `kubectl get ... -o json`) its elements are yielded instead.
-    def each_json_item(io, k8s: false)
-      return enum_for(:each_json_item, io, k8s: k8s) unless block_given?
-      each_json(io) do |item|
-        if k8s && item.is_a?(Hash) && item.key?("items")
-          item.fetch("items").each { |i| yield i }
-        else
-          yield item
+    # An enumerable of items parsed from a JSON stream. In k8s mode, if a value
+    # has an "items" key (e.g. `kubectl get ... -o json`) its elements are the items instead.
+    def json_items(io, k8s: false)
+      Enumerator.new do |yielder|
+        each_json(io) do |item|
+          if k8s && item.is_a?(Hash) && item.key?("items")
+            item.fetch("items").each { |i| yielder << i }
+          else
+            yielder << item
+          end
         end
       end
     end

From 30f67cbe6b352ce18ecd6aca0222ece8091f70e5 Mon Sep 17 00:00:00 2001
From: Michael Grosser <michael@grosser.it>
Date: Thu, 25 Jun 2026 18:46:03 -0700
Subject: [PATCH 10/10] fast

---
 Readme.md        |  3 +--
 bin/pru          | 17 +++++++++++++----
 lib/pru.rb       | 41 +++++++++++++++--------------------------
 spec/pru_spec.rb |  5 +++--
 4 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/Readme.md b/Readme.md
index f09eda4..1077ae7 100644
--- a/Readme.md
+++ b/Readme.md
@@ -49,8 +49,7 @@ plainly so it pipes nicely into other tools.
 
 ## Kubernetes - each item
 
-Like `--json`, but if the value has an `"items"` key (as `kubectl ... -o json`
-returns) its elements are iterated instead.
+Like `--json`, but iterates `"items"` key (as `kubectl ... -o json` returns).
 
     # list pod names
     kubectl get pods -A -o json | pru --k8s 'dig("metadata", "name")'
diff --git a/bin/pru b/bin/pru
index 9a03502..6d18b82 100755
--- a/bin/pru
+++ b/bin/pru
@@ -57,6 +57,7 @@ map, reduce = ARGV
 reduce ||= options[:reduce]
 map = 'true' if !map || map.empty?
 
+# reading from file or stdin ?
 if options[:file]
   output_lines = []
   input = File.read(options[:file])
@@ -66,9 +67,9 @@ else
   input = $stdin
 end
 
-# dump write as JSON ?
+# output as JSON ?
 if options[:json]
-  require 'json'
+  require 'json' # also used by --k8s, which sets :json
   output_format = lambda do |out|
     case out
     when Hash, Array then JSON.pretty_generate(out)
@@ -77,6 +78,7 @@ if options[:json]
   end
 end
 
+# collect results into list or print them
 collector = lambda do |line|
   line = output_format.call(line) if output_format
   if output_lines
@@ -90,9 +92,15 @@ collector = lambda do |line|
   end
 end
 
-items = if options[:json]
-  Pru.json_items(input, k8s: options[:k8s])
+# find all items (ideally lazy so we can stream)
+items = if options[:k8s]
+  # single document (e.g. `kubectl get ... -o json`) -> parse once and iterate its items
+  JSON.parse(input.read).fetch("items")
+elsif options[:json]
+  # lazy stream of JSON values
+  Pru.each_json(input)
 else
+  # plain lines, chomped, lazily so streaming/head still work
   input.each_line.lazy.map { |line| line.chomp }
 end
 
@@ -104,6 +112,7 @@ else
   Pru.map(items, map) { |out| collector.call out }
 end
 
+# write back to file if requested
 if options[:file]
   content = output_lines.join(newline)
   content << newline if trailing_newline
diff --git a/lib/pru.rb b/lib/pru.rb
index 69d6b7e..8ca2a3c 100644
--- a/lib/pru.rb
+++ b/lib/pru.rb
@@ -21,17 +21,24 @@ def reduce(array, code)
       array.instance_exec(&compile(code))
     end
 
-    # An enumerable of items parsed from a JSON stream. In k8s mode, if a value
-    # has an "items" key (e.g. `kubectl get ... -o json`) its elements are the items instead.
-    def json_items(io, k8s: false)
+    # An enumerable of JSON values parsed from a stream (newline-delimited or multiline),
+    # parsed lazily so we process as input arrives, by accumulating lines until the buffer
+    # forms a complete value.
+    # TODO: this is not very efficient, but keeping track of opening/closing braces might be ugly too
+    def each_json(io)
       Enumerator.new do |yielder|
-        each_json(io) do |item|
-          if k8s && item.is_a?(Hash) && item.key?("items")
-            item.fetch("items").each { |i| yielder << i }
-          else
-            yielder << item
+        buffer = +""
+        io.each_line do |line|
+          buffer << line
+          begin
+            item = JSON.parse(buffer)
+          rescue JSON::ParserError
+            next
           end
+          yielder << item
+          buffer = +""
         end
+        raise JSON::ParserError, "unexpected trailing input: #{buffer.strip}" unless buffer.strip.empty?
       end
     end
 
@@ -40,23 +47,5 @@ def json_items(io, k8s: false)
     def compile(code)
       eval("proc { |i| #{code} }", TOPLEVEL_BINDING, __FILE__, __LINE__)
     end
-
-    # Parse a stream of concatenated JSON values (newline-delimited or multiline)
-    # by accumulating lines until the buffer forms a complete value.
-    # TODO: this is not very efficient, but keeping track of opening/closing braces might be ugly too
-    def each_json(io)
-      buffer = +""
-      io.each_line do |line|
-        buffer << line
-        begin
-          item = JSON.parse(buffer)
-        rescue JSON::ParserError
-          next
-        end
-        yield item
-        buffer = +""
-      end
-      raise JSON::ParserError, "unexpected trailing input: #{buffer.strip}" unless buffer.strip.empty?
-    end
   end
 end
diff --git a/spec/pru_spec.rb b/spec/pru_spec.rb
index 25260b3..1a1bd0d 100644
--- a/spec/pru_spec.rb
+++ b/spec/pru_spec.rb
@@ -166,8 +166,9 @@
       `printf '{"items":[{"metadata":{"name":"a"}},{"metadata":{"name":"b"}}]}\n' | ./bin/pru --k8s 'dig("metadata", "name")'`.should == "a\nb\n"
     end
 
-    it "behaves like --json when there is no items key" do
-      `printf '{"metadata":{"name":"solo"}}\n' | ./bin/pru --k8s 'dig("metadata", "name")'`.should == "solo\n"
+    it "fails when there is no items key" do
+      `printf '{"metadata":{"name":"solo"}}\n' | ./bin/pru --k8s 'dig("metadata", "name")' 2>&1`.should include("key not found")
+      $?.success?.should == false
     end
 
     it "reduces over the items" do