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pidfile.go
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pidfile.go
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// Copyright 2021 Chaos Mesh Authors.
//
// 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.
//
// Package pidfile provides structure and helper functions to create and remove
// PID file. A PID file is usually a file used to store the process ID of a
// running process.
//
// Copyright Moby
// Licensed under the Apache License, Version 2.0 (the "License")
package pidfile
import (
"fmt"
"os"
"path/filepath"
"strconv"
"strings"
"github.com/pkg/errors"
)
// PIDFile is a file used to store the process ID of a running process.
type PIDFile struct {
path string
}
func processExists(pid int) bool {
if _, err := os.Stat(filepath.Join("/proc", strconv.Itoa(pid))); err == nil {
return true
}
return false
}
func checkPIDFileAlreadyExists(path string) error {
if pidByte, err := os.ReadFile(path); err == nil {
pidString := strings.TrimSpace(string(pidByte))
if pid, err := strconv.Atoi(pidString); err == nil {
if processExists(pid) {
return errors.Errorf("pid file found, ensure docker is not running or delete %s", path)
}
}
}
return nil
}
// New creates a PIDfile using the specified path.
func New(path string) (*PIDFile, error) {
if err := checkPIDFileAlreadyExists(path); err != nil {
return nil, err
}
// Note MkdirAll returns nil if a directory already exists
if err := os.MkdirAll(filepath.Dir(path), os.FileMode(0755)); err != nil {
return nil, err
}
if err := os.WriteFile(path, []byte(fmt.Sprintf("%d", os.Getpid())), 0644); err != nil {
return nil, err
}
return &PIDFile{path: path}, nil
}
// Remove removes the PIDFile.
func (file PIDFile) Remove() error {
return os.Remove(file.path)
}