add -k<name> and sort by multiple columns support, fixes #34

lib/helpers.go

@@ -99,6 +99,19 @@ func PrepareTransposerColumns(conf *cfg.Config, data *Tabdata) error {
 	return nil
 }
 
+// output option, prepare -k1,2 sort fields
+func PrepareSortColumns(conf *cfg.Config, data *Tabdata) error {
+	// -c columns
+	usecolumns, err := PrepareColumnVars(conf.SortByColumn, data)
+	if err != nil {
+		return err
+	}
+
+	conf.UseSortByColumn = usecolumns
+
+	return nil
+}
+
 func PrepareColumnVars(columns string, data *Tabdata) ([]int, error) {
 	if columns == "" {
 		return nil, nil

lib/io.go

@@ -48,6 +48,11 @@ func ProcessFiles(conf *cfg.Config, args []string) error {
 		return err
 	}
 
+	err = PrepareSortColumns(conf, &data)
+	if err != nil {
+		return err
+	}
+
 	err = PrepareColumns(conf, &data)
 	if err != nil {
 		return err

lib/printer.go

@@ -33,15 +33,17 @@ import (
 )
 
 func printData(writer io.Writer, conf cfg.Config, data *Tabdata) {
-	// add numbers to headers and remove this we're not interested in
+	//  Sort   the  data  first,  before   headers+entries  are  being
+	// reduced. That way the user can specify any valid column to sort
+	// by, independently if it's being used for display or not.
+	sortTable(conf, data)
+
+	// add numbers to headers and remove those we're not interested in
 	numberizeAndReduceHeaders(conf, data)
 
 	// remove unwanted columns, if any
 	reduceColumns(conf, data)
 
-	// sort the data
-	sortTable(conf, data)
-
 	switch conf.OutputMode {
 	case cfg.Extended:
 		printExtendedData(writer, conf, data)

lib/printer_test.go

@@ -63,7 +63,7 @@ var tests = []struct {
 	name string // so we can identify which one fails, can be the same
 	// for multiple tests, because flags will be appended to the name
 	sortby    string // empty == default
-	column    int    // sort by this column, 0 == default first or NO Sort
+	column    int    // sort by this column (numbers start by 1)
 	desc      bool   // sort in descending order, default == ascending
 	nonum     bool   // hide numbering
 	mode      int    // shell, orgtbl, etc. empty == default: ascii
@@ -162,7 +162,7 @@ DURATION(2): 33d12h
 
 	//------------------------ SORT TESTS
 	{
-		name:   "sortbycolumn",
+		name:   "sortbycolumn3",
 		column: 3,
 		sortby: "numeric",
 		desc:   false,
@@ -173,7 +173,7 @@ beta   	1d10h5m1s  	33      	3/1/2014
 alpha  	4h35m      	170     	2013-Feb-03`,
 	},
 	{
-		name:   "sortbycolumn",
+		name:   "sortbycolumn4",
 		column: 4,
 		sortby: "time",
 		desc:   false,
@@ -184,7 +184,7 @@ alpha  	4h35m      	170     	2013-Feb-03
 beta   	1d10h5m1s  	33      	3/1/2014`,
 	},
 	{
-		name:   "sortbycolumn",
+		name:   "sortbycolumn2",
 		column: 2,
 		sortby: "duration",
 		desc:   false,
@@ -251,15 +251,14 @@ DURATION(2)	WHEN(4)
 
 func TestPrinter(t *testing.T) {
 	for _, testdata := range tests {
-		testname := fmt.Sprintf("print-sortcol-%d-desc-%t-sortby-%s-mode-%d-usecolumns-%s",
-			testdata.column, testdata.desc, testdata.sortby, testdata.mode, testdata.usecolstr)
+		testname := fmt.Sprintf("print-%s-%d-desc-%t-sortby-%s-mode-%d-usecolumns-%s",
+			testdata.name, testdata.column, testdata.desc, testdata.sortby, testdata.mode, testdata.usecolstr)
 		t.Run(testname, func(t *testing.T) {
 			// replaces os.Stdout, but we ignore it
 			var writer bytes.Buffer
 
 			// cmd flags
 			conf := cfg.Config{
-				SortByColumn:   testdata.column,
 				SortDescending: testdata.desc,
 				SortMode:       testdata.sortby,
 				OutputMode:     testdata.mode,
@@ -268,6 +267,10 @@ func TestPrinter(t *testing.T) {
 				NoColor:        true,
 			}
 
+			if testdata.column > 0 {
+				conf.UseSortByColumn = []int{testdata.column}
+			}
+
 			conf.ApplyDefaults()
 
 			// the test checks the len!

lib/sort.go

@@ -18,6 +18,7 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package lib
 
 import (
+	"cmp"
 	"regexp"
 	"sort"
 	"strconv"
@@ -27,34 +28,41 @@ import (
 )
 
 func sortTable(conf cfg.Config, data *Tabdata) {
-	if conf.SortByColumn <= 0 {
+	if len(conf.UseSortByColumn) == 0 {
 		// no sorting wanted
 		return
 	}
 
-	// slightly modified here to match internal array indicies
-	col := conf.SortByColumn
-
-	col-- // ui starts counting by 1, but use 0 internally
-
 	// sanity checks
 	if len(data.entries) == 0 {
 		return
 	}
 
-	if col >= len(data.headers) {
-		// fall back to default column
-		col = 0
-	}
-
 	// actual sorting
 	sort.SliceStable(data.entries, func(i, j int) bool {
-		return compare(&conf, data.entries[i][col], data.entries[j][col])
+		// holds the result of a sort of one column
+		comparators := []int{}
+
+		// iterate over all columns to be sorted, conf.SortMode must be identical!
+		for _, column := range conf.UseSortByColumn {
+			comparators = append(comparators, compare(&conf, data.entries[i][column-1], data.entries[j][column-1]))
+		}
+
+		// return the combined result
+		res := cmp.Or(comparators...)
+
+		switch res {
+		case 0:
+			return true
+		default:
+			return false
+		}
+
 	})
 }
 
 // config is not modified here, but it would be inefficient to copy it every loop
-func compare(conf *cfg.Config, left string, right string) bool {
+func compare(conf *cfg.Config, left string, right string) int {
 	var comp bool
 
 	switch conf.SortMode {
@@ -88,7 +96,12 @@ func compare(conf *cfg.Config, left string, right string) bool {
 		comp = !comp
 	}
 
-	return comp
+	switch comp {
+	case true:
+		return 0
+	default:
+		return 1
+	}
 }
 
 /*

lib/sort_test.go

@@ -53,18 +53,18 @@ func TestCompare(t *testing.T) {
 		mode string
 		a    string
 		b    string
-		want bool
+		want int
 		desc bool
 	}{
 		// ascending
-		{"numeric", "10", "20", true, false},
-		{"duration", "2d4h5m", "45m", false, false},
-		{"time", "12/24/2022", "1/1/1970", false, false},
+		{"numeric", "10", "20", 0, false},
+		{"duration", "2d4h5m", "45m", 1, false},
+		{"time", "12/24/2022", "1/1/1970", 1, false},
 
 		// descending
-		{"numeric", "10", "20", false, true},
-		{"duration", "2d4h5m", "45m", true, true},
-		{"time", "12/24/2022", "1/1/1970", true, true},
+		{"numeric", "10", "20", 1, true},
+		{"duration", "2d4h5m", "45m", 0, true},
+		{"time", "12/24/2022", "1/1/1970", 0, true},
 	}
 
 	for _, testdata := range tests {
@@ -75,7 +75,7 @@ func TestCompare(t *testing.T) {
 			c := cfg.Config{SortMode: testdata.mode, SortDescending: testdata.desc}
 			got := compare(&c, testdata.a, testdata.b)
 			if got != testdata.want {
-				t.Errorf("got %t, want %t", got, testdata.want)
+				t.Errorf("got %d, want %d", got, testdata.want)
 			}
 		})
 	}