update

README

go-update

This package simplifies self updating build in go-update

Package update provides functionality to implement secure, self-updating Go programs (or other single-file targets) A program can update itself by replacing its executable file with a new version.

Example of updating from a URL:

import (
    "fmt"
    "net/http"

    "github.com/inconshreveable/go-update"
)

func doUpdate(url string) error {
    resp, err := http.Get(url)
    if err != nil {
        return err
    }
    defer resp.Body.Close()
    err := update.Apply(resp.Body, update.Options{})
    if err != nil {
        // error handling
    }
    return err
}

Features

• Cross platform support (Windows too!)
• Checksum verification
• Support for updating arbitrary files

License

Apache

Documentation

Index

• func Apply(update io.Reader, opts Options) error
• func RollbackError(err error) error
• type Options

Functions

func Apply

func Apply(update io.Reader, opts Options) error

Apply performs an update of the current executable (or opts.TargetFile, if set) with the contents of the given io.Reader.

Apply performs the following actions to ensure a safe cross-platform update:

2. If configured, computes the checksum of the new executable and verifies it matches.

4. Creates a new file, /path/to/.target.new with the TargetMode with the contents of the updated file

5. Renames /path/to/target to /path/to/.target.old

6. Renames /path/to/.target.new to /path/to/target

7. If the final rename is successful, deletes /path/to/.target.old, returns no error. On Windows, the removal of /path/to/target.old always fails, so instead Apply hides the old file instead.

8. If the final rename fails, attempts to roll back by renaming /path/to/.target.old back to /path/to/target.

If the roll back operation fails, the file system is left in an inconsistent state (betweet steps 5 and 6) where there is no new executable file and the old executable file could not be be moved to its original location. In this case you should notify the user of the bad news and ask them to recover manually. Applications can determine whether the rollback failed by calling RollbackError, see the documentation on that function for additional detail.

func RollbackError

func RollbackError(err error) error

RollbackError takes an error value returned by Apply and returns the error, if any, that occurred when attempting to roll back from a failed update. Applications should always call this function on any non-nil errors returned by Apply.

If no rollback was needed or if the rollback was successful, RollbackError returns nil, otherwise it returns the error encountered when trying to roll back.

Types

type Options

type Options struct {
	// TargetPath defines the path to the file to update.
	// The emptry string means 'the executable file of the running program'.
	TargetPath string

	// Create TargetPath replacement with this file mode. If zero, defaults to 0755.
	TargetMode os.FileMode

	// Checksum of the new binary to verify against. If nil, no checksum or signature verification is done.
	Checksum []byte
}