Updated README

Makefile

@@ -8,6 +8,6 @@ vet: fmt
 buildLib: vet
 	go build -gcflags="all=-N -l" ./...
 buildCmd: buildLib
-	go build -C cmd/ -gcflags="all=-N -l" -o re ./...
+	go build -C kg/ -gcflags="all=-N -l" -o kg ./...
 test: buildCmd
 	go test -v ./...

README.md

@@ -15,3 +15,7 @@ It also includes features not present in regexp, such as lookarounds and backref
 The syntax is, for the most part, a superset of Go's regexp. A full overview of the syntax can be found [here](https://pkg.go.dev/gitea.twomorecents.org/Rockingcool/kleingrep/regex#hdr-Syntax).
 
 __For more information, see https://pkg.go.dev/gitea.twomorecents.org/Rockingcool/kleingrep/regex__.
+
+### How it works
+
+I've written about the inner workings of the engine [on my blog](https://twomorecents.org/writing-regex-engine/index.html).

kg/main.go

@@ -61,6 +61,11 @@ func main() {
 		panic("Invalid match number to print.")
 	}
 
+	// Enable lineFlag if lineNumFlag is enabled
+	if *lineNumFlag {
+		*lineFlag = true
+	}
+
 	// Process:
 	// 1. Convert regex into postfix notation (Shunting-Yard algorithm)
 	// 		a. Add explicit concatenation operators to facilitate this
@@ -68,11 +73,11 @@ func main() {
 	// 3. Run the string against the NFA
 
 	if len(flag.Args()) < 1 { // flag.Args() also strips out program name
-		fmt.Println("ERROR: Missing cmdline args")
+		fmt.Printf("%s: ERROR: Missing cmdline args\n", os.Args[0])
 		os.Exit(22)
 	}
 	if *recursiveFlag && len(flag.Args()) < 2 { // File/Directory must be provided with '-r'
-		fmt.Println("ERROR: Missing cmdline args")
+		fmt.Printf("%s: ERROR: Missing cmdline args\n", os.Args[0])
 		os.Exit(22)
 	}
 	var re string
@@ -87,10 +92,20 @@ func main() {
 		for _, inputFilename := range inputFilenames {
 			inputFile, err := os.Open(inputFilename)
 			if err != nil {
-				fmt.Printf("%s: No such file or directory\n", flag.Args()[1])
+				fmt.Printf("%s: %s: No such file or directory\n", os.Args[0], inputFilename)
-				os.Exit(2)
+			} else {
+				fileStat, err := inputFile.Stat()
+				if err != nil {
+					fmt.Printf("%v\n", err)
+					os.Exit(2)
+				} else {
+					if fileStat.Mode().IsDir() {
+						fmt.Printf("%s: %s: Is a directory\n", os.Args[0], inputFilename)
+					} else {
+						inputFiles = append(inputFiles, inputFile)
+					}
+				}
 			}
-			inputFiles = append(inputFiles, inputFile)
 		}
 	}
 
@@ -108,6 +123,7 @@ func main() {
 	}
 
 	for _, inputFile := range inputFiles {
+		lineNum = 0
 		reader := bufio.NewReader(inputFile)
 		linesRead = false
 		for true {
@@ -202,7 +218,12 @@ func main() {
 				if !(*invertFlag) && len(matchIndices) == 0 || *invertFlag && len(matchIndices) > 0 {
 					continue
 				} else {
-					color.New(color.FgMagenta).Fprintf(out, "%s: ", inputFile.Name()) // Print filename
+					if *recursiveFlag || len(flag.Args()) > 2 { // If we have 2 args, then we're only searching 1 file. We should only print the filename if there's more than 1 file.
+						color.New(color.FgMagenta).Fprintf(out, "%s:", inputFile.Name()) // Print filename
+					}
+					if *lineNumFlag {
+						color.New(color.FgGreen).Fprintf(out, "%d:", lineNum) // Print filename
+					}
 				}
 			}
 

regex/compile.go

@@ -47,6 +47,7 @@ func (re *Reg) UnmarshalText(text []byte) error {
 	return err
 }
 
+// Longest makes future searches prefer the longest branch of an alternation, as opposed to the leftmost branch.
 func (re *Reg) Longest() {
 	re.preferLongest = true
 }