Ability to run in background

main.go

@@ -1,36 +1,78 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"net"
 	"os"
 	"os/exec"
+	"strconv"
 )
 
 var outPort int
 
 func init() {
 	var err error
-	outPort, err = getFreePort()
+
+	outPort, err = checkExistingProcess()
+	if err == nil && isPortListening(outPort) {
+		fmt.Printf("Process is already running on port %d\n", outPort)
+		return
+	}
+
+	// No existing process found or not listening, start a new one
+	outPort, err := getFreePort()
 	if err != nil {
 		panic("Can't get free port")
 	}
+
+	args := os.Args
+	bg := os.Getenv("NOHUP") == "1"
+
 	// Check if there are additional arguments
-	if len(os.Args) > 1 {
-		cmd := exec.Command(os.Args[1], os.Args[2:]...)
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
-		cmd.Env = os.Environ()
-		cmd.Env = append(cmd.Env, fmt.Sprintf("PORT=%d", outPort))
+	if len(args) > 1 {
+		if bg {
+			var out bytes.Buffer
+			var stderr bytes.Buffer
+			cmdd := generateBgCmd(args[1], args[2:]...)
+			cmd := exec.Command("bash", "-c", cmdd)
+			cmd.Stdout = &out
+			cmd.Stderr = &stderr
+			cmd.Env = os.Environ()
+			cmd.Env = append(cmd.Env, fmt.Sprintf("PORT=%d", outPort))
+			err = cmd.Run()
+			if err != nil {
+				fmt.Printf("Error starting command: %v\n", err)
+				os.Exit(1)
+			}
+			pid, err := strconv.Atoi(out.String())
+			if nil != err {
+				fmt.Printf("Error starting command: %v\n", err)
+				os.Exit(1)
+			}
+			if pid == 0 {
+				fmt.Printf("invalid PID of 0")
+				os.Exit(1)
+			}
+			writePidPortFile(pid, outPort)
+			fmt.Printf("Started process %s with PID %d in background\n", args[1], pid)
+		} else {
+			cmd := exec.Command(args[1], args[2:]...)
+			cmd.Stdout = os.Stdout
+			cmd.Stderr = os.Stderr
+			cmd.Env = os.Environ()
+			cmd.Env = append(cmd.Env, fmt.Sprintf("PORT=%d", outPort))
 
-		// Start the specified command
-		err := cmd.Start()
-		if err != nil {
-			fmt.Printf("Error starting command: %v\n", err)
-			os.Exit(1)
+			// Start the specified command
+			err := cmd.Start()
+			if err != nil {
+				fmt.Printf("Error starting command: %v\n", err)
+				os.Exit(1)
+			}
+			pid := cmd.Process.Pid
+			fmt.Printf("Started process %s with PID %d\n", args[1], pid)
 		}
 
-		fmt.Printf("Started process %s with PID %d\n", os.Args[1], cmd.Process.Pid)
 	}
 }
 

util.go

@@ -1,9 +1,15 @@
 package main
 
 import (
+	"fmt"
 	"net"
 	"net/http"
+	"os"
+	"path/filepath"
 	"regexp"
+	"strconv"
+	"strings"
+	"syscall"
 	"time"
 )
 
@@ -31,3 +37,67 @@ func filterInvalidHeaders(headers http.Header) {
 		}
 	}
 }
+
+func getPidFile() string {
+	return filepath.Join(os.Getenv("HOME"), "tmp", "app.pid")
+}
+
+func checkExistingProcess() (int, error) {
+	data, err := os.ReadFile(getPidFile())
+	if err != nil {
+		return 0, err
+	}
+
+	fields := strings.Split(string(data), ":")
+	if len(fields) != 2 {
+		return 0, fmt.Errorf("invalid pid/port file format")
+	}
+
+	pid, err := strconv.Atoi(fields[0])
+	if err != nil {
+		return 0, fmt.Errorf("invalid PID format: %v", err)
+	}
+
+	port, err := strconv.Atoi(fields[1])
+	if err != nil {
+		return 0, fmt.Errorf("invalid port format: %v", err)
+	}
+
+	if processExists(pid) {
+		return port, nil
+	}
+	return 0, fmt.Errorf("no running process found")
+}
+
+func processExists(pid int) bool {
+	process, err := os.FindProcess(pid)
+	if err != nil {
+		return false
+	}
+	err = process.Signal(syscall.Signal(0))
+	return err == nil
+}
+
+func isPortListening(port int) bool {
+	conn, err := net.Dial("tcp", fmt.Sprintf("127.0.0.1:%d", port))
+	if err != nil {
+		return false
+	}
+	conn.Close()
+	return true
+}
+
+func writePidPortFile(pid, port int) {
+	err := os.WriteFile(getPidFile(), []byte(fmt.Sprintf("%d:%d", pid, port)), 0644)
+	if err != nil {
+		fmt.Printf("Failed to write PID/port file: %v\n", err)
+	}
+}
+
+func generateBgCmd(name string, arg ...string) string {
+	return fmt.Sprintf(
+		"nohup %s %s < /dev/null &>$HOME/tmp/app.log & echo -n $! | awk '/[0-9]+$/{ printf $0 }'",
+		name,
+		strings.Join(arg, " "),
+	)
+}