internal/addrfd/addrfd.go

   1 package addrfd
   2
   3 import (
   4         "flag"
   5         "log"
   6         "os"
   7 )
   8
   9 var (
  10         addrfd = flag.Int("addrfd", -1, "File descriptor on which to print the picked address")
  11 )
  12
  13 // MustWrite communicates listening address addr to the parent process via the
  14 // file descriptor number passed to -addrfd, if any. It must be called precisely
  15 // once.
  16 func MustWrite(addr string) {
  17         if *addrfd == -1 {
  18                 return
  19         }
  20         log.Printf("%s is listening on %s", os.Args[0], addr)
  21         f := os.NewFile(uintptr(*addrfd), "")
  22         if _, err := f.Write([]byte(addr)); err != nil {
  23                 log.Fatal(err)
  24         }
  25         if err := f.Close(); err != nil {
  26                 log.Fatal(err)
  27         }
  28 }