Added support for line num flag

cmd/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
@@ -87,7 +92,7 @@ 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: No such file or directory\n", inputFilename)
 				os.Exit(2)
 			}
 			inputFiles = append(inputFiles, inputFile)
@@ -108,6 +113,7 @@ func main() {
 	}
 
 	for _, inputFile := range inputFiles {
+		lineNum = 0
 		reader := bufio.NewReader(inputFile)
 		linesRead = false
 		for true {
@@ -202,8 +208,13 @@ func main() {
 				if !(*invertFlag) && len(matchIndices) == 0 || *invertFlag && len(matchIndices) > 0 {
 					continue
 				} else {
+					if len(inputFiles) > 1 { // Don't need to print file name if there's only one file
 						color.New(color.FgMagenta).Fprintf(out, "%s:", inputFile.Name()) // Print filename
 					}
+					if *lineNumFlag {
+						color.New(color.FgGreen).Fprintf(out, "%d:", lineNum) // Print filename
+					}
+				}
 			}
 
 			// If we are substituting, we need a different behavior, as follows: