README
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cliupdater: Download and keep a Go command-line tool up to date
This is a hack proof-of-concept designed similarly to gcloud's auto-update mechanism. The intention is:
- At most once a day, the command checks if an update is available.
- If there is an update, the tool displays some information about it, and provides a command that can be run to install the update.
- Executing the update command causes the new version to be downloaded and the existing version to be replaced.
This proof-of-concept does this in the simplest way I could think of:
- The binary creates a zero-length hidden "stamp" file with the name
.binary.checkto record the timestamp of the last update check. - On startup, if this file is older than a day, it does an HTTP HEAD request to a download URL (customized for the OS and architecture). This request returns a
Last-Modifiedheader. The value of this header is compared to to the timestamp of the executable. If it is more recent, the tool can print a message. - If the user invokes
Update, it performs an update:- Downloads the file as
.binary.download - Backs up the existing file as
.binary.backup - Renames the download over the existing file
- Downloads the file as
Ideally, the update should be atomic, so multiple concurrent updates or concurrently executing commands will not cause any problems.
TODO
- Verify the downloaded file? E.g. check length or a signature?
- Display release notes or changes?
Documentation
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Index ¶
Constants ¶
const DefaultCheckInterval = 24 * time.Hour
DefaultCheckInterval is the minimum time between checks to see if the program is updated.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Metadata ¶
type Metadata struct {
// The time the source binary was updated.
Updated time.Time
// The difference between the update time of the source binary and the binary on disk.
Diff time.Duration
}
Metadata contains information about the source binary and the binary on disk.
type Updater ¶
type Updater struct {
// URL where the binary can be downloaded.
BaseURL string
// absolute path to the binary to be updated; defaults to the currently executing binary
Path string
// interval between automatic update checks
CheckInterval time.Duration
// Function used to output logs if not nil.
Logf func(message string, args ...interface{})
// Call the new binary with these arguments to "apply" an update. If it fails, the binary
// will not be replaced.
ApplyArgs []string
}
Updater keeps a Go binary up to date with a version available via HTTP(S). This can be used to implement auto-updating command line tools.
func (*Updater) MaybeCheckForUpdate ¶
MaybeCheckForUpdate checks for an update if it has been long enough since the last check. It returns the metadata or an error if it executes a check. It returns a zero Metadata value if it does not check for an update.
Source Files
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