Allow for one-shot command executions

Author: itzg

README.md

@@ -10,13 +10,28 @@ Done.
 
 ## Usage
 
-```bash
-./rcon-cli_* --help
-```
+```text
+rcon-cli is a CLI for attaching to an RCON enabled game server, such as Minecraft.
+Without any additional arguments, the CLI will start an interactive session with
+the RCON server.
 
-For example:
+If arguments are passed into the CLI, then the arguments are sent
+as a single command (joined by spaces), the response is displayed,
+and the CLI will exit.
 
-```bash
-./rcon-cli_darwin_amd64 --host localhost --port 25575 --password test
-```
+Usage:
+  rcon-cli [flags] [RCON command ...]
+
+Examples:
 
+rcon-cli --host mc1 --port 25575
+rcon-cli --port 25575 stop
+RCON_PORT=25575 rcon-cli stop
+
+
+Flags:
+      --config string     config file (default is $HOME/.rcon-cli.yaml)
+      --host string       RCON server's hostname (default "localhost")
+      --password string   RCON server's password
+      --port int          Server's RCON port (default 27015)
+```

cli/entry.go

@@ -24,6 +24,7 @@ import (
 	"bufio"
 	"io"
 	"fmt"
+	"strings"
 )
 
 func Start(hostPort string, password string, in io.Reader, out io.Writer) {
@@ -64,3 +65,29 @@ func Start(hostPort string, password string, in io.Reader, out io.Writer) {
 		fmt.Fprintln(os.Stderr, "reading standard input:", err)
 	}
 }
+
+func Execute(hostPort string, password string, out io.Writer, command ...string) {
+	remoteConsole, err := rcon.Dial(hostPort, password)
+	if err != nil {
+		log.Fatal("Failed to connect to RCON server", err)
+	}
+	defer remoteConsole.Close()
+
+	preparedCmd := strings.Join(command, " ")
+	reqId, err := remoteConsole.Write(preparedCmd)
+
+	resp, respReqId, err := remoteConsole.Read()
+	if err != nil {
+		if err == io.EOF {
+			return
+		}
+		fmt.Fprintln(os.Stderr, "Failed to read command:", err.Error())
+		return
+	}
+
+	if reqId != respReqId {
+		fmt.Fprintln(out, "Weird. This response is for another request.")
+	}
+
+	fmt.Fprintln(out, resp)
+}

cmd/root.go

@@ -31,12 +31,32 @@ var (
 
 // RootCmd represents the base command when called without any subcommands
 var RootCmd = &cobra.Command{
-	Use:   "rcon-cli",
+	Use:   "rcon-cli [flags] [RCON command ...]",
 	Short: "A CLI for attaching to an RCON enabled game server",
-	Long:  ``,
+	Example: `
+rcon-cli --host mc1 --port 25575
+rcon-cli --port 25575 stop
+RCON_PORT=25575 rcon-cli stop
+`,
+	Long:  `
+rcon-cli is a CLI for attaching to an RCON enabled game server, such as Minecraft.
+Without any additional arguments, the CLI will start an interactive session with
+the RCON server.
+
+If arguments are passed into the CLI, then the arguments are sent
+as a single command (joined by spaces), the response is displayed,
+and the CLI will exit.
+`,
 	Run:   func(cmd *cobra.Command, args []string) {
+
 		hostPort := net.JoinHostPort(viper.GetString("host"), strconv.Itoa(viper.GetInt("port")))
-		cli.Start(hostPort, viper.GetString("password"), os.Stdin, os.Stdout)
+		password := viper.GetString("password")
+
+		if len(args) == 0 {
+			cli.Start(hostPort, password, os.Stdin, os.Stdout)
+		} else {
+			cli.Execute(hostPort, password, os.Stdout, args...)
+		}
 	},
 }