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// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build !windows
// +build !windows
// Package activation implements primitives for systemd socket activation.
package activation
import (
"os"
"strconv"
"strings"
"syscall"
)
const (
// listenFdsStart corresponds to `SD_LISTEN_FDS_START`.
listenFdsStart = 3
)
// Files returns a slice containing a `os.File` object for each
// file descriptor passed to this process via systemd fd-passing protocol.
//
// The order of the file descriptors is preserved in the returned slice.
// `unsetEnv` is typically set to `true` in order to avoid clashes in
// fd usage and to avoid leaking environment flags to child processes.
func Files(unsetEnv bool) []*os.File {
if unsetEnv {
defer os.Unsetenv("LISTEN_PID")
defer os.Unsetenv("LISTEN_FDS")
defer os.Unsetenv("LISTEN_FDNAMES")
}
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
}
names := strings.Split(os.Getenv("LISTEN_FDNAMES"), ":")
files := make([]*os.File, 0, nfds)
for fd := listenFdsStart; fd < listenFdsStart+nfds; fd++ {
syscall.CloseOnExec(fd)
name := "LISTEN_FD_" + strconv.Itoa(fd)
offset := fd - listenFdsStart
if offset < len(names) && len(names[offset]) > 0 {
name = names[offset]
}
files = append(files, os.NewFile(uintptr(fd), name))
}
return files
}
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