Remove empty go.sum

README.md

@@ -5,7 +5,7 @@ Ubiquiti UPS units seem to use a somewhat non-standard format for responses from
 
 ## Usage
 1. Enable the NUT server on your Ubiquiti UniFi-connected UPS unit.
-    - Do **NOT** enable the "Login Credential" option!
+    - The "Login Credential" setting is optional; if enabled, be sure to use the .Authenticate() method immediately after dialing!
 2. This module can now be used to get variables from your UPS's NUT server as follows:
 ```go
 package main
@@ -18,12 +18,29 @@ import (
 
 func main() {
 	host := "IP:PORT"
-	upsID := "UPS-ID"
+	username := "username"
+	password := "password"
+	
+	// connect to NUT server
 	client, err := nut.Dial(host)
 	if err != nil {
 		panic(err)
 	}
-	err = client.GetListVar(upsID)
+	
+	// authenticate (if "Login Credential" is enabled on the NUT server)
+	err = client.Authenticate(username, password)
+	if err != nil {
+		panic(err)
+	}
+	
+	// auto-detect UPS ID
+	err = client.AutomaticallySetID()
+	if err != nil {
+		panic(err)
+	}
+	
+	// list all variables from your UPS
+	err = client.ListVar()
 	if err != nil {
 		panic(err)
 	}
@@ -32,3 +49,5 @@ func main() {
 	}
 }
 ```
+
+This module also features a .GetVar() method for retrieving the value of only one variable.

go.mod

@@ -1,3 +1,3 @@
 module github.com/rwinkhart/uni-nut
 
-go 1.25.2
+go 1.25.5

nut.go

@@ -11,6 +11,8 @@ import (
 type Client struct {
 	conn        net.Conn
 	br          *bufio.Reader
+	upsID       string
+	upsIDLength int
 }
 
 // Global map to be updated by GetListVar and read by the importing program.
@@ -36,9 +38,48 @@ func (c *Client) Close() error {
 	return c.conn.Close()
 }
 
-// GetListVar updates NutKeyValMap with the current status of all variables from <upsID>.
+// Authenticate logs into credential-protected sessions.
-func (c *Client) GetListVar(upsID string) error {
+// If authentication is enabled on your NUT server, run
-	cmd := "LIST VAR \"" + upsID + "\""
+// this immediately after dialing.
+func (c *Client) Authenticate(username, password string) error {
+	var err error
+	if err = c.write("USERNAME " + username + "\nPASSWORD " + password); err != nil {
+		return err
+	}
+	_, err = c.clearBuffer("OK L", "")
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// AutomaticallySetID detects the ID of the connected UPS.
+// This only works when there is only one UPS per
+// NUT server, which is the case with UniFi UPS units.
+func (c *Client) AutomaticallySetID() error {
+	if err := c.write("LIST UPS"); err != nil {
+		return err
+	}
+	l, err := c.clearBuffer("END", "UPS")
+	if err != nil {
+		return err
+	}
+	lSplit := strings.Split(l, " ")
+	c.upsID = strings.Join(lSplit[1:len(lSplit)-2], " ")
+	c.upsIDLength = len(strings.Split(c.upsID, " "))
+	return nil
+}
+
+// ManuallySetID allows the user to specify the UPS ID
+// manually if auto-detection is not desired.
+func (c *Client) ManuallySetID(upsID string) {
+	c.upsID = upsID
+	c.upsIDLength = len(strings.Split(upsID, " "))
+}
+
+// ListVar updates NutKeyValMap with the current status of all variables from the target UPS.
+func (c *Client) ListVar() error {
+	cmd := "LIST VAR \"" + c.upsID + "\""
 	if err := c.write(cmd); err != nil {
 		return err
 	}
@@ -46,9 +87,9 @@ func (c *Client) GetListVar(upsID string) error {
 	if err != nil {
 		return err
 	}
-	expected := "BEGIN " + cmd
+	expectedPrefix := "BEGIN LIST VAR"
-	if l != expected {
+	if !strings.HasPrefix(l, expectedPrefix) {
-		return fmt.Errorf("pre-loop error: expected %q, got %q", expected, l)
+		return fmt.Errorf("pre-loop error: expected prefix %q, got line %q", expectedPrefix, l)
 	}
 
 outer:
@@ -60,7 +101,7 @@ outer:
 		lSplit := strings.Split(l, " ")
 		switch lSplit[0] {
 		case "VAR":
-			NutKeyValMap[strings.Trim(lSplit[2], "\"")] = strings.Trim(strings.Join(lSplit[3:], " "), "\"")
+			NutKeyValMap[lSplit[1+c.upsIDLength]] = strings.Trim(strings.Join(lSplit[2+c.upsIDLength:], " "), "\"")
 		default:
 			break outer
 		}
@@ -68,9 +109,25 @@ outer:
 	return nil
 }
 
-// newClient wraps an existing net.Conn.
+// GetVar returns the value of the specified variable for the target UPS.
+func (c *Client) GetVar(varName string) (string, error) {
+	if err := c.write("GET VAR \"" + c.upsID + "\" \"" + varName + "\""); err != nil {
+		return "", err
+	}
+	l, err := c.read()
+	if err != nil {
+		return "", err
+	}
+	lSplit := strings.Split(l, " ")
+	if len(lSplit) < 4 {
+		return "", fmt.Errorf("invalid response to GET VAR; check your UPS ID")
+	}
+	value := strings.Trim(strings.Join(lSplit[2+c.upsIDLength:], " "), "\"")
+	return value, nil
+}
+
 func newClient(conn net.Conn) *Client {
-	return &Client{conn, bufio.NewReader(conn)}
+	return &Client{conn, bufio.NewReader(conn), "", 0}
 }
 
 func (c *Client) write(s string) error {
@@ -88,3 +145,19 @@ func (c *Client) read() (string, error) {
 	}
 	return l, nil
 }
+
+func (c *Client) clearBuffer(tillPrefix, storePrefix string) (string, error) {
+	var stored string
+	for {
+		l, err := c.read()
+		if err != nil {
+			return "", err
+		}
+		if storePrefix != "" && strings.HasPrefix(l, storePrefix) {
+			stored = l
+		} else if strings.HasPrefix(l, tillPrefix) {
+			break
+		}
+	}
+	return stored, nil
+}