exiftool

README

A thin wrapper around ExifTool

Fork of ncruces/go-exiftool adding channeled output with custom splitters (NewServerCh, CommandCh).

Server (ExifTool with -stay_open) in this fork:

• a per-command timeout (SetTimeout): a command that hangs kills and restarts ExifTool;
• killed processes are reaped (no zombies);
• no orphans (Unix): ExifTool never exits on its own at the end of its argfile — it polls for more, 100 times a second, forever — so a program that dies without Close (SIGKILL, a crash) would leave it running. Every ExifTool gets a watchdog: a shell blocked on a pipe whose only writer is the Go process; when the process dies the pipe closes and the watchdog kills ExifTool at once. Both are the Go process's children and reaped by it (no zombies, also as PID 1); the watchdog is stopped as soon as ExifTool is reaped, so it never signals a reused pid. Not on Windows.

This uses the excellent ExifTool by Phil Harvey:

• https://exiftool.org/
• https://github.com/exiftool/exiftool

dist_unix.sh and dist_windows.sh build minimal, self-contained distros of ExifTool for both Unix (Linux/macOS/etc) and Windows. Use Git BASH to run the Windows script.

The Windows version uses Strawberry Perl:

• https://strawberryperl.com/
• https://github.com/StrawberryPerl

Documentation

Overview

Package exiftool provides a thin wrapper around ExifTool.

Index

• Variables
• func Command(stdin io.Reader, arg ...string) (stdout []byte, err error)
• func CommandContext(ctx context.Context, stdin io.Reader, arg ...string) (stdout []byte, err error)
• func DefaultSplitter(data []byte, atEOF bool) (advance int, token []byte, err error)
• func Unmarshal(data []byte, m map[string][]byte) error
• type Server
  • func NewServer(commonArg ...string) (*Server, error)
  • func NewServerCh(chout chan<- string, splitFunc bufio.SplitFunc, commonArg ...string) (*Server, error)
  • func (e *Server) Close() error
  • func (e *Server) Command(arg ...string) ([]byte, error)
  • func (e *Server) CommandCh(arg ...string) error
  • func (e *Server) SetTimeout(d time.Duration)
  • func (e *Server) Shutdown() error

Variables

var (
	Exec   string = "exiftool" // Application to execute.
	Arg1   string              // Optional first argument.
	Config string              // ExifTool config file to use.
)

Configure ExifTool.

var ErrTimeout = errors.New("exiftool: command timed out")

ErrTimeout is returned by Command when ExifTool does not answer within the timeout set by SetTimeout. The ExifTool process is restarted.

Functions

func Command

func Command(stdin io.Reader, arg ...string) (stdout []byte, err error)

Command runs an ExifTool command with the given arguments and stdin and returns its stdout.

func CommandContext

func CommandContext(ctx context.Context, stdin io.Reader, arg ...string) (stdout []byte, err error)

CommandContext is like Command but includes a context.

func DefaultSplitter

func DefaultSplitter(data []byte, atEOF bool) (advance int, token []byte, err error)

func Unmarshal

func Unmarshal(data []byte, m map[string][]byte) error

Unmarshal parses the standard, short or veryShort ExifTool output formats. Loads tag names and values into a map.

Types

type Server

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

Server wraps an instance of ExifTool that can process multiple commands sequentially. Servers avoid the overhead of loading ExifTool for each command. Servers are safe for concurrent use by multiple goroutines.

func NewServer

func NewServer(commonArg ...string) (*Server, error)

NewServer loads a new instance of ExifTool.

func NewServerCh

func NewServerCh(chout chan<- string, splitFunc bufio.SplitFunc, commonArg ...string) (*Server, error)

NewServerCh loads a new instance of ExifTool with output to channel file by file.

func (*Server) Close

func (e *Server) Close() error

Close causes ExifTool to exit immediately and waits until the process is reaped.

func (*Server) Command

func (e *Server) Command(arg ...string) ([]byte, error)

Command runs an ExifTool command with the given arguments and returns its stdout. Commands should neither read from stdin, nor write binary data to stdout.

func (*Server) CommandCh

func (e *Server) CommandCh(arg ...string) error

Command runs an ExifTool command with the given arguments and put its stdout to channel. Commands should neither read from stdin, nor write binary data to stdout.

func (*Server) SetTimeout

func (e *Server) SetTimeout(d time.Duration)

SetTimeout limits how long a single Command may take; 0 (the default) means no limit. On timeout the ExifTool process is killed and restarted and Command returns ErrTimeout, so one broken file cannot block the server forever.

func (*Server) Shutdown

func (e *Server) Shutdown() error

Shutdown gracefully shuts down ExifTool without interrupting any commands, and waits for it to complete.