tail

README

Go package for tail-ing files

This is a fork of the tail library from https://github.com/influxdata/tail

A Go package striving to emulate the features of the BSD tail program.

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

See API documentation.

Log rotation

Tail comes with full support for truncation/move detection as it is designed to work with log rotation tools.

Installing

go get github.com/hpcloud/tail/...

Windows support

This package needs assistance for full Windows support.

Documentation

Index

• Variables
• func OpenFile(name string) (file *os.File, err error)
• type Config
• type Line
  • func NewLine(text string, offset int64) *Line
• type SeekInfo
• type Tail
  • func TailFile(filename string, config Config) (*Tail, error)
  • func (tail *Tail) Cleanup()
  • func (tail *Tail) Stop() error
  • func (tail *Tail) StopAtEOF() error
  • func (tail *Tail) Tell() (offset int64, err error)
  • func (tail *Tail) UnexpectedError() (err error)

Variables

var (
	ErrStop             = errors.New("Tail should now stop")
	ErrDeletedNotReOpen = errors.New("File was deleted, tail should now stop")

	OpenFileCount atomic.Int64
)

Functions

func OpenFile

func OpenFile(name string) (file *os.File, err error)

Types

type Config

type Config struct {
	// File-specifc
	Location    *SeekInfo // Seek to this location before tailing
	ReOpen      bool      // Reopen recreated files (tail -F)
	MustExist   bool      // Fail early if the file does not exist
	Poll        bool      // Poll for file changes instead of using inotify
	Pipe        bool      // Is a named pipe (mkfifo)
	RateLimiter limiter

	// Generic IO
	Follow      bool // Continue looking for new lines (tail -f)
	MaxLineSize int  // If non-zero, split longer lines into multiple lines

	Logger telegraf.Logger

	// Special handling for utf16
	IsUTF16 bool
}

Config is used to specify how a file must be tailed.

type Line

type Line struct {
	Text   string
	Time   time.Time
	Err    error // Error from tail
	Offset int64 // offset of current reader
}

func NewLine

func NewLine(text string, offset int64) *Line

NewLine returns a Line with present time.

type SeekInfo

type SeekInfo struct {
	Offset int64
	Whence int // os.SEEK_*
}

SeekInfo represents arguments to `os.Seek`

type Tail

type Tail struct {
	Filename string
	Lines    chan *Line
	Config

	tomb.Tomb // provides: Done, Kill, Dying

	FileDeletedCh chan bool
	// contains filtered or unexported fields
}

func TailFile

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

TailFile begins tailing the file. Output stream is made available via the `Tail.Lines` channel. To handle errors during tailing, invoke the `Wait` or `Err` method after finishing reading from the `Lines` channel.

func (*Tail) Cleanup

func (tail *Tail) Cleanup()

Cleanup removes inotify watches added by the tail package. This function is meant to be invoked from a process's exit handler. Linux kernel may not automatically remove inotify watches after the process exits.

func (*Tail) Stop

func (tail *Tail) Stop() error

Stop stops the tailing activity.

func (*Tail) StopAtEOF

func (tail *Tail) StopAtEOF() error

StopAtEOF stops tailing as soon as the end of the file is reached. Blocks until tailer is dead and returns reason for death.

func (*Tail) Tell

func (tail *Tail) Tell() (offset int64, err error)

Return the file's current position, like stdio's ftell(). But this value is not very accurate. it may readed one line in the chan(tail.Lines), so it may lost one line.

func (*Tail) UnexpectedError

func (tail *Tail) UnexpectedError() (err error)

A wrapper of tomb Err()