improved command line argument handling

main.go

@@ -12,10 +12,7 @@ import (
 	"github.com/fatih/color"
 )
 
-var (
+var ColorRed = color.New(color.FgRed)
-	FlagOutputFile = flag.String("o", "output.pdf", "output file name")
-	ColorRed       = color.New(color.FgRed)
-)
 
 func main() {
 	flag.Parse()
@@ -25,12 +22,17 @@ func main() {
 		os.Exit(1)
 	}
 
-	inputFilePath := flag.Arg(0)
+	if len(flag.Args()) == 0 {
-	if inputFilePath == "" {
+		ColorRed.Fprintln(os.Stderr, "please provide at least one input file path")
-		ColorRed.Fprintln(os.Stderr, "please provide an input file path")
 		os.Exit(1)
 	}
 
+	for _, inputFilePath := range flag.Args() {
+		Convert(inputFilePath)
+	}
+}
+
+func Convert(inputFilePath string) {
 	inputFile, err := os.Open(inputFilePath)
 	if err != nil {
 		ColorRed.Fprintf(os.Stderr, "input file path could not be read: %s\n", err.Error())
@@ -77,7 +79,8 @@ func main() {
 		tempFile.Close()
 	}
 
-	args := append([]string{"--output", *FlagOutputFile}, tempFiles...)
+	outputFilePath := fmt.Sprintf("%s.pdf", filepath.Base(inputFilePath)[:len(inputFilePath)-len(filepath.Ext(inputFilePath))])
+	args := append([]string{"--output", outputFilePath}, tempFiles...)
 	img2pdf := exec.Command("img2pdf", args...)
 
 	if err := img2pdf.Start(); err != nil {
@@ -89,4 +92,6 @@ func main() {
 		ColorRed.Fprintf(os.Stderr, "img2pdf returned an error: %s\n", err.Error())
 		os.Exit(1)
 	}
+
+	fmt.Println(outputFilePath)
 }