4 files changed, 59 insertions(+), 0 deletions(-)

A README.md
A daemonize/daemonize.go
A daemonize/go.mod
A go.work

@@ 1,3 @@
+# goul
+
+_**go**lang **u**tility **l**ibrary_

@@ 1,50 @@
+package daemonize
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+)
+
+func Daemonize() error {
+	err := syscall.FcntlFlock(os.Stdout.Fd(), syscall.F_SETLKW, &syscall.Flock_t{
+		Type: syscall.F_WRLCK, Whence: 0, Start: 0, Len: 0,
+	})
+	if err != nil {
+		return fmt.Errorf("Failed to lock stdout: %w", err)
+	}
+
+	if os.Getppid() != 1 {
+		// parent; spawns child as daemon
+		binary, err := exec.LookPath(os.Args[0])
+		if err != nil {
+			return fmt.Errorf("Failed to lookup binary: %w", err)
+		}
+		_, err = os.StartProcess(binary, os.Args, &os.ProcAttr{
+			Dir: "", Env: nil,
+			Files: []*os.File{os.Stdin, os.Stdout, os.Stderr}, Sys: nil,
+		})
+		if err != nil {
+			return fmt.Errorf("Failed to start process: %w", err)
+		}
+		os.Exit(0)
+	} else {
+		// start new session
+		_, err := syscall.Setsid()
+		if err != nil {
+			return fmt.Errorf("Failed to create new session: %w", err)
+		}
+		file, err := os.OpenFile("/dev/null", os.O_RDWR, 0)
+		if err != nil {
+			return fmt.Errorf("Failed to open /dev/null: %w", err)
+		}
+		// detach from terminal
+		syscall.Dup2(int(file.Fd()), int(os.Stdin.Fd()))
+		syscall.Dup2(int(file.Fd()), int(os.Stdout.Fd()))
+		syscall.Dup2(int(file.Fd()), int(os.Stderr.Fd()))
+		file.Close()
+	}
+
+	return nil
+}

@@ 1,3 @@
+module dev.gzr.im/goul/daemonize
+
+go 1.20

@@ 1,3 @@
+go 1.20
+
+use ./daemonize