systemd.go

package systemd

import (
        "os"
        "strconv"
        "syscall"
)

const (
        listenFdsStart = 3
)

func ListenFds() []*os.File {
        pid, err := strconv.Atoi(os.Getenv("LISTEN_PID"))
        if err != nil || pid != os.Getpid() {
                return nil
        }
        nfds, err := strconv.Atoi(os.Getenv("LISTEN_FDS"))
        if err != nil || nfds == 0 {
                return nil
        }
        files := []*os.File(nil)
        for fd := listenFdsStart; fd < listenFdsStart+nfds; fd++ {
                syscall.CloseOnExec(fd)
                files = append(files, os.NewFile(uintptr(fd), ""))
        }
        return files
}

Why run an extra fcntl system call just to find out whether you need to set the CLOEXEC flag? Just run syscall.CloseOnExec unconditionally. The result is the same, and you only run one system call per FD.

Good point. I just did a direct translation of sd_listen_fds long ago. I'll update this.