Fantom-foundation/go-lachesis

package utils

import (
    "fmt"
    "os"
    "syscall"

    "github.com/facebookgo/pidfile"
)

func CheckPid(pidfileName string) error {
    pidfile.SetPidfilePath(pidfileName)
    pid, err := pidfile.Read()
    if err == nil && pid > 0 {
        process, err := os.FindProcess(pid)
        if err != nil {
            return fmt.Errorf("failed to find process: %v", err)
        }
        err = process.Signal(syscall.Signal(0))
        if err == nil {
            return fmt.Errorf("perhaps another lachesis is already running with pid %d", pid)
        }
    }

    if err := pidfile.Write(); err != nil {
        return fmt.Errorf("error writing into pidfile: %v", err)
    }

    return nil
}