tail

README

Tail implementation in Go

A Go package striving to emulate the BSD tail program.

t := tail.TailFile("/var/log/nginx.log", tail.Config{Follow: true})
for line := range t.Lines {
    fmt.Println(line.Text)
}

Installing

go get github.com/ActiveState/tail

Building

To build and test the package,

make test

To build the command-line program gotail,

cd cmd/gotail
make
./gotail -h

TODO

• Support arbitrary values for Location

Documentation

Overview

TODO: avoid creating two instances of the fsnotify.Watcher struct

Index

• func Cleanup()
• type Config
• type FileWatcher
• type InotifyFileWatcher
  • func NewInotifyFileWatcher(filename string) *InotifyFileWatcher
  • func (fw *InotifyFileWatcher) BlockUntilExists() error
  • func (fw *InotifyFileWatcher) ChangeEvents() chan bool
• type InotifyTracker
  • func NewInotifyTracker() *InotifyTracker
  • func (t *InotifyTracker) CloseAll()
  • func (t *InotifyTracker) CloseWatcher(w *fsnotify.Watcher) (err error)
  • func (t *InotifyTracker) NewWatcher() (*fsnotify.Watcher, error)
• type Line
• type PollingFileWatcher
  • func NewPollingFileWatcher(filename string) *PollingFileWatcher
  • func (fw *PollingFileWatcher) BlockUntilExists() error
  • func (fw *PollingFileWatcher) ChangeEvents() chan bool
• type Tail
  • func TailFile(filename string, config Config) (*Tail, error)
  • func (tail *Tail) Stop() error

Functions

func Cleanup

func Cleanup()

Cleanup removes open inotify watchers (as the Linux kernel doesn't do it upon process exit).

Types

type Config

type Config struct {
	Location    int  // -n
	Follow      bool // -f
	ReOpen      bool // -F
	MustExist   bool // if false, wait for the file to exist before beginning to tail.
	Poll        bool // if true, do not use inotify but use polling
	MaxLineSize int  // if > 0, limit the line size (rest of the line would be returned as next lines)
}

type FileWatcher

type FileWatcher interface {
	BlockUntilExists() error
	ChangeEvents() chan bool
}

type InotifyFileWatcher

type InotifyFileWatcher struct {
	Filename string
}

FileWatcher monitors file-level events

func NewInotifyFileWatcher

func NewInotifyFileWatcher(filename string) *InotifyFileWatcher

func (*InotifyFileWatcher) BlockUntilExists

func (fw *InotifyFileWatcher) BlockUntilExists() error

BlockUntilExists blocks until the file comes into existence. If the file already exists, then block until it is created again.

func (*InotifyFileWatcher) ChangeEvents

func (fw *InotifyFileWatcher) ChangeEvents() chan bool

ChangeEvents returns a channel that gets updated when the file is ready to be read.

type InotifyTracker

type InotifyTracker struct {
	// contains filtered or unexported fields
}

func NewInotifyTracker

func NewInotifyTracker() *InotifyTracker

func (*InotifyTracker) CloseAll

func (t *InotifyTracker) CloseAll()

func (*InotifyTracker) CloseWatcher

func (t *InotifyTracker) CloseWatcher(w *fsnotify.Watcher) (err error)

func (*InotifyTracker) NewWatcher

func (t *InotifyTracker) NewWatcher() (*fsnotify.Watcher, error)

type Line

type Line struct {
	Text string
	Time time.Time
}

type PollingFileWatcher

type PollingFileWatcher struct {
	Filename string
}

FileWatcher monitors file-level events

func NewPollingFileWatcher

func NewPollingFileWatcher(filename string) *PollingFileWatcher

func (*PollingFileWatcher) BlockUntilExists

func (fw *PollingFileWatcher) BlockUntilExists() error

BlockUntilExists blocks until the file comes into existence. If the file already exists, then block until it is created again.

func (*PollingFileWatcher) ChangeEvents

func (fw *PollingFileWatcher) ChangeEvents() chan bool

ChangeEvents returns a channel that gets updated when the file is ready to be read.

type Tail

type Tail struct {
	Filename string
	Lines    chan *Line
	Config

	tomb.Tomb // provides: Done, Kill, Dying
	// contains filtered or unexported fields
}

func TailFile

func TailFile(filename string, config Config) (*Tail, error)

TailFile channels the lines of a logfile along with timestamp. If end is true, channel only newly added lines. If retry is true, tail the file name (not descriptor) and retry on file open/read errors. func TailFile(filename string, maxlinesize int, end bool, retry bool, useinotify bool) (*Tail, error) {

func (*Tail) Stop

func (tail *Tail) Stop() error