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moby--moby/pkg/pidfile/pidfile.go

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// 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.
package pidfile
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"strings"
"github.com/docker/docker/pkg/system"
)
// PIDFile is a file used to store the process ID of a running process.
type PIDFile struct {
path string
}
func checkPIDFileAlreadyExists(path string) error {
if pidByte, err := ioutil.ReadFile(path); err == nil {
pidString := strings.TrimSpace(string(pidByte))
if pid, err := strconv.Atoi(pidString); err == nil {
if processExists(pid) {
return fmt.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 := system.MkdirAll(filepath.Dir(path), os.FileMode(0755)); err != nil {
return nil, err
}
if err := ioutil.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 {
if err := os.Remove(file.path); err != nil {
return err
}
return nil
}