fix #85: add --auto-headers and --custom-headers

Author: Thomas von Dein

cfg/config.go

@@ -28,7 +28,7 @@ import (
 )
 
 const (
-	Version  = "v1.5.9"
+	Version  = "v1.5.10"
 	MAXPARTS = 2
 )
 
@@ -93,6 +93,8 @@ type Config struct {
 	UseHighlight   bool
 	Interactive    bool
 	InputJSON      bool
+	AutoHeaders    bool
+	CustomHeaders  []string
 
 	SortMode        string
 	SortDescending  bool
@@ -413,6 +415,12 @@ func (conf *Config) PreparePattern(patterns []*Pattern) error {
 	return nil
 }
 
+func (conf *Config) PrepareCustomHeaders(custom string) {
+	if len(custom) > 0 {
+		conf.CustomHeaders = strings.Split(custom, ",")
+	}
+}
+
 // Parse config file.  Ignore if the file doesn't exist  but return an
 // error if it exists but fails to read or parse
 func (conf *Config) ParseConfigfile() error {

cmd/root.go

@@ -59,6 +59,7 @@ func Execute() {
 		ShowCompletion string
 		modeflag       cfg.Modeflag
 		sortmode       cfg.Sortmode
+		headers        string
 	)
 
 	var rootCmd = &cobra.Command{
@@ -91,6 +92,7 @@ func Execute() {
 			conf.CheckEnv()
 			conf.PrepareModeFlags(modeflag)
 			conf.PrepareSortFlags(sortmode)
+			conf.PrepareCustomHeaders(headers)
 
 			wrapE(conf.PrepareFilters())
 
@@ -137,6 +139,10 @@ func Execute() {
 		"Output field separator (' ' for ascii table, ',' for CSV)")
 	rootCmd.PersistentFlags().BoolVarP(&conf.InputJSON, "json", "j", false,
 		"JSON input mode")
+	rootCmd.PersistentFlags().BoolVarP(&conf.AutoHeaders, "auto-headers", "", false,
+		"Generate headers automatically")
+	rootCmd.PersistentFlags().StringVarP(&headers, "custom-headers", "", "",
+		"Custom headers")
 
 	// sort options
 	rootCmd.PersistentFlags().StringVarP(&conf.SortByColumn, "sort-by", "k", "",

cmd/tablizer.go

@@ -22,6 +22,8 @@ SYNOPSIS
           -R, --regex-transposer </from/to/> Apply /search/replace/ regexp to fields given in -T
           -j, --json                         Read JSON input (must be array of hashes)
           -I, --interactive                  Interactively filter and select rows
+              --auto-headers                 Generate headers if there are none present in input
+              --custom-headers a,b,...       Use custom headers, separated by comma
 
         Output Flags (mutually exclusive):
           -X, --extended                     Enable extended output
@@ -517,6 +519,8 @@ Operational Flags:
   -R, --regex-transposer </from/to/> Apply /search/replace/ regexp to fields given in -T
   -j, --json                         Read JSON input (must be array of hashes)
   -I, --interactive                  Interactively filter and select rows
+      --auto-headers                 Generate headers if there are none present in input
+      --custom-headers a,b,...       Use custom headers, separated by comma
 
 Output Flags (mutually exclusive):
   -X, --extended                     Enable extended output

lib/parser.go

@@ -66,6 +66,43 @@ func Parse(conf cfg.Config, input io.Reader) (Tabdata, error) {
 	return data, err
 }
 
+/*
+ * Setup headers,  given headers might  be usable headers or  just the
+ * first row, which we use to  determine how many headers to generate,
+ * if enabled.
+ */
+func SetHeaders(conf cfg.Config, headers []string) []string {
+	if !conf.AutoHeaders && len(conf.CustomHeaders) == 0 {
+		return headers
+	}
+
+	if conf.AutoHeaders {
+		heads := make([]string, len(headers))
+		for idx := range headers {
+			heads[idx] = fmt.Sprintf("%d", idx+1)
+		}
+
+		return heads
+	}
+
+	if len(conf.CustomHeaders) == len(headers) {
+		return conf.CustomHeaders
+	}
+
+	// use as much custom ones we have, generate the remainder
+	heads := make([]string, len(headers))
+
+	for idx := range headers {
+		if idx < len(conf.CustomHeaders) {
+			heads[idx] = conf.CustomHeaders[idx]
+		} else {
+			heads[idx] = fmt.Sprintf("%d", idx+1)
+		}
+	}
+
+	return heads
+}
+
 /*
 Parse CSV input.
 */
@@ -87,7 +124,7 @@ func parseCSV(conf cfg.Config, input io.Reader) (Tabdata, error) {
 	}
 
 	if len(records) >= 1 {
-		data.headers = records[0]
+		data.headers = SetHeaders(conf, records[0])
 		data.columns = len(records)
 
 		for _, head := range data.headers {
@@ -98,9 +135,14 @@ func parseCSV(conf cfg.Config, input io.Reader) (Tabdata, error) {
 			}
 		}
 
-		if len(records) > 1 {
-			data.entries = records[1:]
+		if len(records) >= 1 {
+			if conf.AutoHeaders || len(conf.CustomHeaders) > 0 {
+				data.entries = records
+			} else {
+				data.entries = records[1:]
+			}
 		}
+
 	}
 
 	return data, nil
@@ -128,19 +170,32 @@ func parseTabular(conf cfg.Config, input io.Reader) (Tabdata, error) {
 			data.columns = len(parts)
 
 			// process all header fields
-			for _, part := range parts {
+			firstrow := make([]string, len(parts))
+
+			for idx, part := range parts {
 				// register widest header field
 				headerlen := len(part)
 				if headerlen > data.maxwidthHeader {
 					data.maxwidthHeader = headerlen
 				}
 
 				// register fields data
-				data.headers = append(data.headers, strings.TrimSpace(part))
+				firstrow[idx] = strings.TrimSpace(part)
 
 				// done
 				hadFirst = true
 			}
+
+			data.headers = SetHeaders(conf, firstrow)
+
+			if conf.AutoHeaders || len(conf.CustomHeaders) > 0 {
+				// we do not use generated headers, consider as row
+				if matchPattern(conf, line) == conf.InvertMatch {
+					continue
+				}
+
+				data.entries = append(data.entries, firstrow)
+			}
 		} else {
 			// data processing
 			if matchPattern(conf, line) == conf.InvertMatch {

lib/parser_test.go

@@ -366,6 +366,56 @@ func TestParserSeparators(t *testing.T) {
 	}
 }
 
+func TestParserSetHeaders(t *testing.T) {
+	row := []string{"c", "b", "c", "d", "e"}
+
+	tests := []struct {
+		name   string
+		custom []string
+		expect []string
+		auto   bool
+	}{
+		{
+			name:   "default",
+			expect: row,
+		},
+		{
+			name:   "auto",
+			expect: strings.Split("1 2 3 4 5", " "),
+			auto:   true,
+		},
+		{
+			name:   "custom-complete",
+			custom: strings.Split("A B C D E", " "),
+			expect: strings.Split("A B C D E", " "),
+		},
+		{
+			name:   "custom-too-short",
+			custom: strings.Split("A B", " "),
+			expect: strings.Split("A B 3 4 5", " "),
+		},
+		{
+			name:   "custom-too-long",
+			custom: strings.Split("A B C D E F G", " "),
+			expect: strings.Split("A B C D E", " "),
+		},
+	}
+
+	for _, testdata := range tests {
+		testname := fmt.Sprintf("parse-%s", testdata.name)
+		t.Run(testname, func(t *testing.T) {
+			conf := cfg.Config{
+				AutoHeaders:   testdata.auto,
+				CustomHeaders: testdata.custom,
+			}
+			headers := SetHeaders(conf, row)
+
+			assert.NotNil(t, headers)
+			assert.EqualValues(t, testdata.expect, headers)
+		})
+	}
+}
+
 func wrapValidateParser(conf cfg.Config, input io.Reader) (Tabdata, error) {
 	data, err := Parse(conf, input)
 

tablizer.1

@@ -133,7 +133,7 @@
 .\" ========================================================================
 .\"
 .IX Title "TABLIZER 1"
-.TH TABLIZER 1 "2025-10-09" "1" "User Commands"
+.TH TABLIZER 1 "2025-10-10" "1" "User Commands"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
@@ -160,6 +160,8 @@ tablizer \- Manipulate tabular output of other programs
 \&      \-R, \-\-regex\-transposer </from/to/> Apply /search/replace/ regexp to fields given in \-T
 \&      \-j, \-\-json                         Read JSON input (must be array of hashes)
 \&      \-I, \-\-interactive                  Interactively filter and select rows
+\&          \-\-auto\-headers                 Generate headers if there are none present in input
+\&          \-\-custom\-headers a,b,...       Use custom headers, separated by comma
 \&
 \&    Output Flags (mutually exclusive):
 \&      \-X, \-\-extended                     Enable extended output

tablizer.pod

@@ -21,6 +21,8 @@ tablizer - Manipulate tabular output of other programs
       -R, --regex-transposer </from/to/> Apply /search/replace/ regexp to fields given in -T
       -j, --json                         Read JSON input (must be array of hashes)
       -I, --interactive                  Interactively filter and select rows
+          --auto-headers                 Generate headers if there are none present in input
+          --custom-headers a,b,...       Use custom headers, separated by comma
 
     Output Flags (mutually exclusive):
       -X, --extended                     Enable extended output