From 0b2688c0f16bedbbf956dc9b7ecd411ad1cde0dd Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Fri, 29 Oct 2021 14:14:39 +1100
Subject: [PATCH] Split printer

---
 .gitignore                            |   6 +-
 acceptance_tests/basic.sh             |   2 +-
 acceptance_tests/empty.sh             |   1 +
 acceptance_tests/front-matter.sh      |   1 +
 acceptance_tests/leading-seperator.sh |   1 +
 acceptance_tests/output-format.sh     |   4 +
 acceptance_tests/pretty-print.sh      |   3 +
 acceptance_tests/split-printer.sh     | 157 ++++++++++++++++++++++++++
 cmd/constant.go                       |   2 +
 cmd/evaluate_all_command.go           |   8 +-
 cmd/evalute_sequence_command.go       |   8 +-
 cmd/printer_utils.go                  |  24 ++++
 cmd/root.go                           |   3 +
 pkg/yqlib/operator_encoder_decoder.go |   3 +-
 pkg/yqlib/operators_test.go           |   4 +-
 pkg/yqlib/printer.go                  | 130 ++++++++++++---------
 pkg/yqlib/printer_test.go             |  18 +--
 pkg/yqlib/printer_writer.go           |  81 +++++++++++++
 18 files changed, 385 insertions(+), 71 deletions(-)
 create mode 100755 acceptance_tests/split-printer.sh
 create mode 100644 cmd/printer_utils.go
 create mode 100644 pkg/yqlib/printer_writer.go

diff --git a/.gitignore b/.gitignore
index fac7e030..00b1ab74 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,8 +38,12 @@ parts/
 prime/
 .snapcraft/
 yq*.snap
+
 test.yml
-test2.yml
+test*.yml
+0.yml
+1.yml
+2.yml
 
 
 # man page
diff --git a/acceptance_tests/basic.sh b/acceptance_tests/basic.sh
index f83f9085..dc9069ae 100755
--- a/acceptance_tests/basic.sh
+++ b/acceptance_tests/basic.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 
 setUp() {
-  rm -f test.yml
+  rm test*.yml || true
 }
 
 testBasicEvalRoundTrip() {
diff --git a/acceptance_tests/empty.sh b/acceptance_tests/empty.sh
index d7f344df..7ffb813f 100755
--- a/acceptance_tests/empty.sh
+++ b/acceptance_tests/empty.sh
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 setUp() {
+  rm test*.yml || true
   cat >test.yml <<EOL
 # comment
 EOL
diff --git a/acceptance_tests/front-matter.sh b/acceptance_tests/front-matter.sh
index b02356b5..a9f079be 100755
--- a/acceptance_tests/front-matter.sh
+++ b/acceptance_tests/front-matter.sh
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 setUp() {
+  rm test*.yml || true
   cat >test.yml <<EOL
 ---
 a: apple
diff --git a/acceptance_tests/leading-seperator.sh b/acceptance_tests/leading-seperator.sh
index a8fae4e9..65338b36 100755
--- a/acceptance_tests/leading-seperator.sh
+++ b/acceptance_tests/leading-seperator.sh
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 setUp() {
+  rm test*.yml || true
   cat >test.yml <<EOL
 ---
 a: test
diff --git a/acceptance_tests/output-format.sh b/acceptance_tests/output-format.sh
index a36290b5..35e3b92f 100755
--- a/acceptance_tests/output-format.sh
+++ b/acceptance_tests/output-format.sh
@@ -1,5 +1,9 @@
 #!/bin/bash
 
+setUp() {
+  rm test*.yml || true
+}
+
 testOutputJsonDeprecated() {
   cat >test.yml <<EOL
 a: {b: ["cat"]}
diff --git a/acceptance_tests/pretty-print.sh b/acceptance_tests/pretty-print.sh
index 5ebfed21..9b59ea04 100755
--- a/acceptance_tests/pretty-print.sh
+++ b/acceptance_tests/pretty-print.sh
@@ -1,5 +1,8 @@
 #!/bin/bash
 
+setUp() {
+  rm test*.yml || true
+}
 
 testPrettyPrintWithBooleans() {
   cat >test.yml <<EOL
diff --git a/acceptance_tests/split-printer.sh b/acceptance_tests/split-printer.sh
new file mode 100755
index 00000000..71170422
--- /dev/null
+++ b/acceptance_tests/split-printer.sh
@@ -0,0 +1,157 @@
+#!/bin/bash
+
+setUp() {
+  rm test*.yml || true
+}
+
+testBasicSplitWithName() {
+  cat >test.yml <<EOL
+a: test_doc1
+--- 
+a: test_doc2
+EOL
+
+  ./yq e test.yml -s ".a"
+
+  doc1=$(cat test_doc1.yml)
+  
+  assertEquals "a: test_doc1" "$doc1"
+
+  doc2=$(cat test_doc2.yml)
+  read -r -d '' expectedDoc2 << EOM
+---
+a: test_doc2
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+}
+
+testBasicSplitWithNameEvalAll() {
+  cat >test.yml <<EOL
+a: test_doc1
+--- 
+a: test_doc2
+EOL
+
+  ./yq ea test.yml -s ".a"
+
+  doc1=$(cat test_doc1.yml)
+  
+  assertEquals "a: test_doc1" "$doc1"
+
+  doc2=$(cat test_doc2.yml)
+  read -r -d '' expectedDoc2 << EOM
+---
+a: test_doc2
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+}
+
+testBasicSplitWithIndex() {
+  cat >test.yml <<EOL
+a: test_doc1
+--- 
+a: test_doc2
+EOL
+
+  ./yq e test.yml -s '"test_" + $index'
+
+  doc1=$(cat test_0.yml)
+  
+  assertEquals "a: test_doc1" "$doc1"
+
+  doc2=$(cat test_1.yml)
+  read -r -d '' expectedDoc2 << EOM
+---
+a: test_doc2
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+}
+
+testBasicSplitWithIndexEvalAll() {
+  cat >test.yml <<EOL
+a: test_doc1
+--- 
+a: test_doc2
+EOL
+
+  ./yq ea test.yml -s '"test_" + $index'
+
+  doc1=$(cat test_0.yml)
+  
+  assertEquals "a: test_doc1" "$doc1"
+
+  doc2=$(cat test_1.yml)
+  read -r -d '' expectedDoc2 << EOM
+---
+a: test_doc2
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+}
+
+
+testArraySplitWithNameNoSeparators() {
+  cat >test.yml <<EOL
+- name: test_fred
+  age: 35
+- name: test_catherine
+  age: 37
+EOL
+
+  ./yq e --no-doc -s ".name"  ".[]" test.yml 
+
+  doc1=$(cat test_fred.yml)
+  read -r -d '' expectedDoc1 << EOM
+name: test_fred
+age: 35
+EOM
+
+  assertEquals "$expectedDoc1" "$doc1"
+
+  doc2=$(cat test_catherine.yml)
+  read -r -d '' expectedDoc2 << EOM
+name: test_catherine
+age: 37
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+}
+
+testArraySplitWithNameNoSeparatorsEvalAll() {
+  cat >test.yml <<EOL
+- name: test_fred
+  age: 35
+- name: test_catherine
+  age: 37
+EOL
+
+cat >test2.yml <<EOL
+- name: test_mike
+  age: 564
+EOL
+
+  ./yq ea --no-doc -s ".name"  ".[]" test.yml test2.yml
+
+  doc1=$(cat test_fred.yml)
+  read -r -d '' expectedDoc1 << EOM
+name: test_fred
+age: 35
+EOM
+
+  assertEquals "$expectedDoc1" "$doc1"
+
+  doc2=$(cat test_catherine.yml)
+  read -r -d '' expectedDoc2 << EOM
+name: test_catherine
+age: 37
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+
+
+  doc3=$(cat test_mike.yml)
+  read -r -d '' expectedDoc3 << EOM
+name: test_mike
+age: 564
+EOM
+  assertEquals "$expectedDoc3" "$doc3"
+}
+
+source ./scripts/shunit2
\ No newline at end of file
diff --git a/cmd/constant.go b/cmd/constant.go
index 9b6369c9..0b921410 100644
--- a/cmd/constant.go
+++ b/cmd/constant.go
@@ -21,4 +21,6 @@ var prettyPrint = false
 // can be either "" (off), "extract" or "process"
 var frontMatter = ""
 
+var splitFileExp = ""
+
 var completedSuccessfully = false
diff --git a/cmd/evaluate_all_command.go b/cmd/evaluate_all_command.go
index bb3f04bf..d8dc02c8 100644
--- a/cmd/evaluate_all_command.go
+++ b/cmd/evaluate_all_command.go
@@ -70,6 +70,10 @@ func evaluateAll(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("Write inplace flag only applicable when giving an expression and at least one file")
 	}
 
+	if writeInplace && splitFileExp != "" {
+		return fmt.Errorf("Write inplace cannot be used with split file")
+	}
+
 	if writeInplace {
 		// only use colors if its forced
 		colorsEnabled = forceColor
@@ -96,7 +100,9 @@ func evaluateAll(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	printer := yqlib.NewPrinter(out, format, unwrapScalar, colorsEnabled, indent, !noDocSeparators)
+	printerWriter := configurePrinterWriter(format, out)
+
+	printer := yqlib.NewPrinter(printerWriter, format, unwrapScalar, colorsEnabled, indent, !noDocSeparators)
 
 	if frontMatter != "" {
 		frontMatterHandler := yqlib.NewFrontMatterHandler(args[firstFileIndex])
diff --git a/cmd/evalute_sequence_command.go b/cmd/evalute_sequence_command.go
index c5daea88..c2b32d79 100644
--- a/cmd/evalute_sequence_command.go
+++ b/cmd/evalute_sequence_command.go
@@ -83,6 +83,10 @@ func evaluateSequence(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("Write inplace flag only applicable when giving an expression and at least one file")
 	}
 
+	if writeInplace && splitFileExp != "" {
+		return fmt.Errorf("Write inplace cannot be used with split file")
+	}
+
 	if writeInplace {
 		// only use colors if its forced
 		colorsEnabled = forceColor
@@ -106,7 +110,9 @@ func evaluateSequence(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	printer := yqlib.NewPrinter(out, format, unwrapScalar, colorsEnabled, indent, !noDocSeparators)
+	printerWriter := configurePrinterWriter(format, out)
+
+	printer := yqlib.NewPrinter(printerWriter, format, unwrapScalar, colorsEnabled, indent, !noDocSeparators)
 
 	streamEvaluator := yqlib.NewStreamEvaluator()
 
diff --git a/cmd/printer_utils.go b/cmd/printer_utils.go
new file mode 100644
index 00000000..9f638bff
--- /dev/null
+++ b/cmd/printer_utils.go
@@ -0,0 +1,24 @@
+package cmd
+
+import (
+	"io"
+
+	"github.com/mikefarah/yq/v4/pkg/yqlib"
+)
+
+func configurePrinterWriter(format yqlib.PrinterOutputFormat, out io.Writer) yqlib.PrinterWriter {
+
+	var printerWriter yqlib.PrinterWriter
+
+	if splitFileExp != "" {
+		colorsEnabled = forceColor
+		splitExp, err := yqlib.NewExpressionParser().ParseExpression(splitFileExp)
+		if err != nil {
+			return nil
+		}
+		printerWriter = yqlib.NewMultiPrinterWriter(splitExp, format)
+	} else {
+		printerWriter = yqlib.NewSinglePrinterWriter(out)
+	}
+	return printerWriter
+}
diff --git a/cmd/root.go b/cmd/root.go
index e7b4a116..11471d27 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -63,6 +63,9 @@ See https://mikefarah.gitbook.io/yq/ for detailed documentation and examples.`,
 	rootCmd.PersistentFlags().BoolVarP(&forceNoColor, "no-colors", "M", false, "force print with no colors")
 	rootCmd.PersistentFlags().StringVarP(&frontMatter, "front-matter", "f", "", "(extract|process) first input as yaml front-matter. Extract will pull out the yaml content, process will run the expression against the yaml content, leaving the remaining data intact")
 	rootCmd.PersistentFlags().BoolVarP(&leadingContentPreProcessing, "header-preprocess", "", true, "Slurp any header comments and separators before processing expression. This is a workaround for go-yaml to persist header content properly.")
+
+	rootCmd.PersistentFlags().StringVarP(&splitFileExp, "split-exp", "s", "", "print each result (or doc) into a file named (exp). [exp] argument must return a string. You can use $index in the expression as the result counter.")
+
 	rootCmd.AddCommand(
 		createEvaluateSequenceCommand(),
 		createEvaluateAllCommand(),
diff --git a/pkg/yqlib/operator_encoder_decoder.go b/pkg/yqlib/operator_encoder_decoder.go
index e20a5166..33887797 100644
--- a/pkg/yqlib/operator_encoder_decoder.go
+++ b/pkg/yqlib/operator_encoder_decoder.go
@@ -13,7 +13,8 @@ import (
 func yamlToString(candidate *CandidateNode, prefs encoderPreferences) (string, error) {
 	var output bytes.Buffer
 	log.Debug("printing with indent: %v", prefs.indent)
-	printer := NewPrinter(bufio.NewWriter(&output), prefs.format, true, false, prefs.indent, true)
+
+	printer := NewPrinterWithSingleWriter(bufio.NewWriter(&output), prefs.format, true, false, prefs.indent, true)
 	err := printer.PrintResults(candidate.AsList())
 	return output.String(), err
 }
diff --git a/pkg/yqlib/operators_test.go b/pkg/yqlib/operators_test.go
index b450e0c6..af7b1d7a 100644
--- a/pkg/yqlib/operators_test.go
+++ b/pkg/yqlib/operators_test.go
@@ -107,7 +107,7 @@ func copyFromHeader(title string, out *os.File) error {
 
 func formatYaml(yaml string, filename string) string {
 	var output bytes.Buffer
-	printer := NewPrinter(bufio.NewWriter(&output), YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(bufio.NewWriter(&output), YamlOutputFormat, true, false, 2, true)
 
 	node, err := NewExpressionParser().ParseExpression(".. style= \"\"")
 	if err != nil {
@@ -216,7 +216,7 @@ func documentInput(w *bufio.Writer, s expressionScenario) (string, string) {
 func documentOutput(t *testing.T, w *bufio.Writer, s expressionScenario, formattedDoc string, formattedDoc2 string) {
 	var output bytes.Buffer
 	var err error
-	printer := NewPrinter(bufio.NewWriter(&output), YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(bufio.NewWriter(&output), YamlOutputFormat, true, false, 2, true)
 
 	node, err := NewExpressionParser().ParseExpression(s.expression)
 	if err != nil {
diff --git a/pkg/yqlib/printer.go b/pkg/yqlib/printer.go
index 1d8031d3..3ac4bcee 100644
--- a/pkg/yqlib/printer.go
+++ b/pkg/yqlib/printer.go
@@ -44,7 +44,7 @@ type resultsPrinter struct {
 	colorsEnabled      bool
 	indent             int
 	printDocSeparators bool
-	writer             io.Writer
+	printerWriter      PrinterWriter
 	firstTimePrinting  bool
 	previousDocIndex   uint
 	previousFileIndex  int
@@ -53,9 +53,13 @@ type resultsPrinter struct {
 	appendixReader     io.Reader
 }
 
-func NewPrinter(writer io.Writer, outputFormat PrinterOutputFormat, unwrapScalar bool, colorsEnabled bool, indent int, printDocSeparators bool) Printer {
+func NewPrinterWithSingleWriter(writer io.Writer, outputFormat PrinterOutputFormat, unwrapScalar bool, colorsEnabled bool, indent int, printDocSeparators bool) Printer {
+	return NewPrinter(NewSinglePrinterWriter(writer), outputFormat, unwrapScalar, colorsEnabled, indent, printDocSeparators)
+}
+
+func NewPrinter(printerWriter PrinterWriter, outputFormat PrinterOutputFormat, unwrapScalar bool, colorsEnabled bool, indent int, printDocSeparators bool) Printer {
 	return &resultsPrinter{
-		writer:             writer,
+		printerWriter:      printerWriter,
 		outputFormat:       outputFormat,
 		unwrapScalar:       unwrapScalar,
 		colorsEnabled:      colorsEnabled,
@@ -98,15 +102,57 @@ func (p *resultsPrinter) writeString(writer io.Writer, txt string) error {
 	return errorWriting
 }
 
-func (p *resultsPrinter) safelyFlush(writer *bufio.Writer) {
-	if err := writer.Flush(); err != nil {
-		log.Error("Error flushing writer!")
-		log.Error(err.Error())
+func (p *resultsPrinter) processLeadingContent(mappedDoc *CandidateNode, writer io.Writer) error {
+	if strings.Contains(mappedDoc.Node.HeadComment, "$yqLeadingContent$") {
+		log.Debug("headcommentwas %v", mappedDoc.Node.HeadComment)
+		log.Debug("finished headcomment")
+		reader := bufio.NewReader(strings.NewReader(mappedDoc.Node.HeadComment))
+		mappedDoc.Node.HeadComment = ""
+
+		for {
+
+			readline, errReading := reader.ReadString('\n')
+			if errReading != nil && errReading != io.EOF {
+				return errReading
+			}
+			if strings.Contains(readline, "$yqLeadingContent$") {
+				// skip this
+
+			} else if strings.Contains(readline, "$yqDocSeperator$") {
+				if p.printDocSeparators {
+					if err := p.writeString(writer, "---\n"); err != nil {
+						return err
+					}
+				}
+			} else if p.outputFormat == YamlOutputFormat {
+				if err := p.writeString(writer, readline); err != nil {
+					return err
+				}
+			}
+
+			if errReading == io.EOF {
+				if readline != "" {
+					// the last comment we read didn't have a new line, put one in
+					if err := p.writeString(writer, "\n"); err != nil {
+						return err
+					}
+				}
+				break
+			}
+		}
+
 	}
+	return nil
 }
 
 func (p *resultsPrinter) PrintResults(matchingNodes *list.List) error {
 	log.Debug("PrintResults for %v matches", matchingNodes.Len())
+
+	if matchingNodes.Len() == 0 {
+		log.Debug("no matching results, nothing to print")
+		return nil
+	}
+
 	if p.outputFormat != YamlOutputFormat {
 		explodeOp := Operation{OperationType: explodeOpType}
 		explodeNode := ExpressionNode{Operation: &explodeOp}
@@ -117,13 +163,6 @@ func (p *resultsPrinter) PrintResults(matchingNodes *list.List) error {
 		matchingNodes = context.MatchingNodes
 	}
 
-	bufferedWriter := bufio.NewWriter(p.writer)
-	defer p.safelyFlush(bufferedWriter)
-
-	if matchingNodes.Len() == 0 {
-		log.Debug("no matching results, nothing to print")
-		return nil
-	}
 	if p.firstTimePrinting {
 		node := matchingNodes.Front().Value.(*CandidateNode)
 		p.previousDocIndex = node.Document
@@ -132,72 +171,53 @@ func (p *resultsPrinter) PrintResults(matchingNodes *list.List) error {
 	}
 
 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
+
 		mappedDoc := el.Value.(*CandidateNode)
 		log.Debug("-- print sep logic: p.firstTimePrinting: %v, previousDocIndex: %v, mappedDoc.Document: %v, printDocSeparators: %v", p.firstTimePrinting, p.previousDocIndex, mappedDoc.Document, p.printDocSeparators)
 
+		writer, errorWriting := p.printerWriter.GetWriter(mappedDoc)
+		if errorWriting != nil {
+			return errorWriting
+		}
+
 		commentStartsWithSeparator := strings.Contains(mappedDoc.Node.HeadComment, "$yqLeadingContent$\n$yqDocSeperator$")
 
 		if (p.previousDocIndex != mappedDoc.Document || p.previousFileIndex != mappedDoc.FileIndex) && p.printDocSeparators && !commentStartsWithSeparator {
 			log.Debug("-- writing doc sep")
-			if err := p.writeString(bufferedWriter, "---\n"); err != nil {
+			if err := p.writeString(writer, "---\n"); err != nil {
 				return err
 			}
 		}
 
-		if strings.Contains(mappedDoc.Node.HeadComment, "$yqLeadingContent$") {
-			log.Debug("headcommentwas %v", mappedDoc.Node.HeadComment)
-			log.Debug("finished headcomment")
-			reader := bufio.NewReader(strings.NewReader(mappedDoc.Node.HeadComment))
-			mappedDoc.Node.HeadComment = ""
-
-			for {
-
-				readline, errReading := reader.ReadString('\n')
-				if errReading != nil && errReading != io.EOF {
-					return errReading
-				}
-				if strings.Contains(readline, "$yqLeadingContent$") {
-					// skip this
-
-				} else if strings.Contains(readline, "$yqDocSeperator$") {
-					if p.printDocSeparators {
-						if err := p.writeString(bufferedWriter, "---\n"); err != nil {
-							return err
-						}
-					}
-				} else if p.outputFormat == YamlOutputFormat {
-					if err := p.writeString(bufferedWriter, readline); err != nil {
-						return err
-					}
-				}
-
-				if errReading == io.EOF {
-					if readline != "" {
-						// the last comment we read didn't have a new line, put one in
-						if err := p.writeString(bufferedWriter, "\n"); err != nil {
-							return err
-						}
-					}
-					break
-				}
-			}
-
+		if err := p.processLeadingContent(mappedDoc, writer); err != nil {
+			return err
 		}
 
-		if err := p.printNode(mappedDoc.Node, bufferedWriter); err != nil {
+		if err := p.printNode(mappedDoc.Node, writer); err != nil {
 			return err
 		}
 
 		p.previousDocIndex = mappedDoc.Document
+		if err := writer.Flush(); err != nil {
+			return err
+		}
 	}
 
 	if p.appendixReader != nil && p.outputFormat == YamlOutputFormat {
+		writer, err := p.printerWriter.GetWriter(nil)
+		if err != nil {
+			return err
+		}
+
 		log.Debug("Piping appendix reader...")
 		betterReader := bufio.NewReader(p.appendixReader)
-		_, err := io.Copy(bufferedWriter, betterReader)
+		_, err = io.Copy(writer, betterReader)
 		if err != nil {
 			return err
 		}
+		if err := writer.Flush(); err != nil {
+			return err
+		}
 	}
 
 	return nil
diff --git a/pkg/yqlib/printer_test.go b/pkg/yqlib/printer_test.go
index cda5270f..56acd5a8 100644
--- a/pkg/yqlib/printer_test.go
+++ b/pkg/yqlib/printer_test.go
@@ -36,7 +36,7 @@ func nodeToList(candidate *CandidateNode) *list.List {
 func TestPrinterMultipleDocsInSequence(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -74,7 +74,7 @@ func TestPrinterMultipleDocsInSequence(t *testing.T) {
 func TestPrinterMultipleDocsInSequenceWithLeadingContent(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -116,7 +116,7 @@ func TestPrinterMultipleDocsInSequenceWithLeadingContent(t *testing.T) {
 func TestPrinterMultipleFilesInSequence(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -163,7 +163,7 @@ func TestPrinterMultipleFilesInSequence(t *testing.T) {
 func TestPrinterMultipleFilesInSequenceWithLeadingContent(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -213,7 +213,7 @@ func TestPrinterMultipleFilesInSequenceWithLeadingContent(t *testing.T) {
 func TestPrinterMultipleDocsInSinglePrint(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -232,7 +232,7 @@ func TestPrinterMultipleDocsInSinglePrint(t *testing.T) {
 func TestPrinterMultipleDocsInSinglePrintWithLeadingDoc(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -261,7 +261,7 @@ a: coconut
 func TestPrinterMultipleDocsInSinglePrintWithLeadingDocTrailing(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
@@ -287,7 +287,7 @@ a: coconut
 func TestPrinterScalarWithLeadingCont(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)
-	printer := NewPrinter(writer, YamlOutputFormat, true, false, 2, true)
+	printer := NewPrinterWithSingleWriter(writer, YamlOutputFormat, true, false, 2, true)
 
 	node, err := NewExpressionParser().ParseExpression(".a")
 	if err != nil {
@@ -314,7 +314,7 @@ func TestPrinterMultipleDocsJson(t *testing.T) {
 	var writer = bufio.NewWriter(&output)
 	// note printDocSeparators is true, it should still not print document separators
 	// when outputing JSON.
-	printer := NewPrinter(writer, JsonOutputFormat, true, false, 0, true)
+	printer := NewPrinterWithSingleWriter(writer, JsonOutputFormat, true, false, 0, true)
 
 	inputs, err := readDocuments(strings.NewReader(multiDocSample), "sample.yml", 0)
 	if err != nil {
diff --git a/pkg/yqlib/printer_writer.go b/pkg/yqlib/printer_writer.go
new file mode 100644
index 00000000..d4292323
--- /dev/null
+++ b/pkg/yqlib/printer_writer.go
@@ -0,0 +1,81 @@
+package yqlib
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+
+	"gopkg.in/yaml.v3"
+)
+
+type PrinterWriter interface {
+	GetWriter(node *CandidateNode) (*bufio.Writer, error)
+}
+
+type singlePrinterWriter struct {
+	bufferedWriter *bufio.Writer
+}
+
+func NewSinglePrinterWriter(writer io.Writer) PrinterWriter {
+	return &singlePrinterWriter{
+		bufferedWriter: bufio.NewWriter(writer),
+	}
+}
+
+func (sp *singlePrinterWriter) GetWriter(node *CandidateNode) (*bufio.Writer, error) {
+	return sp.bufferedWriter, nil
+}
+
+type multiPrintWriter struct {
+	treeNavigator  DataTreeNavigator
+	nameExpression *ExpressionNode
+	extension      string
+	index          int
+}
+
+func NewMultiPrinterWriter(expression *ExpressionNode, format PrinterOutputFormat) PrinterWriter {
+	extension := "yml"
+
+	switch format {
+	case JsonOutputFormat:
+		extension = "json"
+	case PropsOutputFormat:
+		extension = "properties"
+	}
+
+	return &multiPrintWriter{
+		nameExpression: expression,
+		extension:      extension,
+		treeNavigator:  NewDataTreeNavigator(),
+		index:          0,
+	}
+}
+
+func (sp *multiPrintWriter) GetWriter(node *CandidateNode) (*bufio.Writer, error) {
+	name := ""
+
+	indexVariableNode := yaml.Node{Kind: yaml.ScalarNode, Tag: "!!int", Value: fmt.Sprintf("%v", sp.index)}
+	indexVariableCandidate := CandidateNode{Node: &indexVariableNode}
+
+	context := Context{MatchingNodes: node.AsList()}
+	context.SetVariable("index", indexVariableCandidate.AsList())
+	result, err := sp.treeNavigator.GetMatchingNodes(context, sp.nameExpression)
+	if err != nil {
+		return nil, err
+	}
+	if result.MatchingNodes.Len() > 0 {
+		name = result.MatchingNodes.Front().Value.(*CandidateNode).Node.Value
+	}
+	name = fmt.Sprintf("%v.%v", name, sp.extension)
+
+	f, err := os.Create(name)
+
+	if err != nil {
+		return nil, err
+	}
+	sp.index = sp.index + 1
+
+	return bufio.NewWriter(f), nil
+
+}