Merge pull request #22 from AkihiroSuda/stdio

use stdio for default input and output

go-md2man.1.md

@@ -11,6 +11,8 @@ go-md2man 1 "January 2015" go-md2man "User Manual"
   go-md2man converts standard markdown formatted documents into manpages. It is
   written purely in Go so as to reduce dependencies on 3rd party libs.
 
+  By default, the input is stdin and the output is stdout.
+
 # Example
   Convert the markdown file "go-md2man.1.md" into a manpage.
 

md2man.go

@@ -9,16 +9,20 @@ import (
 	"github.com/cpuguy83/go-md2man/md2man"
 )
 
-var inFilePath = flag.String("in", "", "Path to file to be processed")
-var outFilePath = flag.String("out", "", "Path to output processed file")
+var inFilePath = flag.String("in", "", "Path to file to be processed (default: stdin)")
+var outFilePath = flag.String("out", "", "Path to output processed file (default: stdout)")
 
 func main() {
+	var err error
 	flag.Parse()
 
-	inFile, err := os.Open(*inFilePath)
-	if err != nil {
-		fmt.Println(err)
-		os.Exit(1)
+	inFile := os.Stdin
+	if *inFilePath != "" {
+		inFile, err = os.Open(*inFilePath)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
 	}
 	defer inFile.Close()
 
@@ -30,12 +34,15 @@ func main() {
 
 	out := md2man.Render(doc)
 
-	outFile, err := os.Create(*outFilePath)
-	if err != nil {
-		fmt.Println(err)
-		os.Exit(1)
+	outFile := os.Stdout
+	if *outFilePath != "" {
+		outFile, err = os.Create(*outFilePath)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+		defer outFile.Close()
 	}
-	defer outFile.Close()
 	_, err = outFile.Write(out)
 	if err != nil {
 		fmt.Println(err)