add input hostname from files option '-f'

README.md

@@ -26,6 +26,7 @@ Usage of nssh:
 -i=false: handle stdin
 -p=false: add hostname to line prefix
 -t=[]: target hostname
+-f=[]: target hostname from files
 -v=false: show version
 ```
 
@@ -43,4 +44,16 @@ Pass nssh's stdin to remote command. Use `-i` option.
 $ echo foo | nssh -i -t host-web-001 -t host-web-002 cat
 foo
 foo
+
+```
+
+Target hosts from file. Use `-f` option.
+
+```
+$ cat hosts.txt
+host-web-001
+host-web-002
+$ nssh -f hosts.txt cat /var/log/nginx/access.log
+12.34.567.890 - - [06/Oct/2015:15:52:42 +0900] "-" 400 0 "-" "-"
+12.34.567.890 - - [06/Oct/2015:15:52:43 +0900] "GET / HTTP/1.1" 200 133 "-" "Mozilla/5.0 (Windows NT 5.1; rv:9.0.1) Gecko/20100101 Firefox/9.0.1"
 ```

nssh.go

@@ -30,8 +30,10 @@ func (s *strslice) Set(v string) error {
 
 func main() {
 	var targets strslice
+	var filenames strslice
 	var showVersion bool
 	flag.Var(&targets, "t", "target hostname")
+	flag.Var(&filenames, "f", "target hostname from file")
 	flag.BoolVar(&addPrefix, "p", false, "add hostname to line prefix")
 	flag.BoolVar(&showVersion, "v", false, "show version")
 	flag.BoolVar(&handleStdin, "i", false, "handle STDIN")
@@ -40,6 +42,9 @@ func main() {
 		fmt.Println("version:", version)
 		return
 	}
+	if len(filenames) > 0 {
+		getHostFromFiles(&targets, &filenames)
+	}
 
 	command := flag.Args()
 	if len(command) < 1 {
@@ -148,3 +153,21 @@ func writeInput(src chan []byte, dest io.WriteCloser, host string) {
 		}
 	}
 }
+
+func getHostFromFiles(targets *strslice, filenames *strslice) {
+	for _, filename := range *filenames {
+		f, err := os.Open(filename)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "[error]", filename, err)
+			return
+		}
+		defer f.Close()
+		scanner := bufio.NewScanner(f)
+		for scanner.Scan() {
+			targets.Set(scanner.Text())
+		}
+		if err = scanner.Err(); err != nil {
+			fmt.Fprintln(os.Stderr, "[error]", err)
+		}
+	}
+}