https://github.com/jdrews/go-tailer
go-tailer is a Go library designed to help you tail files in a similar fashion to tail -f
https://github.com/jdrews/go-tailer
follow go golang golang-library log logfile logs tail tailing
Last synced: 6 months ago
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go-tailer is a Go library designed to help you tail files in a similar fashion to tail -f
- Host: GitHub
- URL: https://github.com/jdrews/go-tailer
- Owner: jdrews
- License: apache-2.0
- Created: 2023-05-25T04:34:17.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2025-11-25T03:29:58.000Z (7 months ago)
- Last Synced: 2025-11-28T13:13:56.786Z (7 months ago)
- Topics: follow, go, golang, golang-library, log, logfile, logs, tail, tailing
- Language: Go
- Homepage:
- Size: 2.32 MB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
- Security: SECURITY.md
- Authors: AUTHORS
- Notice: NOTICE
Awesome Lists containing this project
README
#  go-tailer #
go-tailer is a Go library designed to help you tail files in a similar fashion to `tail -f`
[](https://opensource.org/licenses/Apache-2.0)
[](https://pkg.go.dev/github.com/jdrews/go-tailer)
[](https://sonarcloud.io/project/overview?id=jdrews_go-tailer)
[](https://goreportcard.com/report/github.com/jdrews/go-tailer)
Built off the wonderful work by [@fstab](https://github.com/fstab) in the [grok_exporter/tailer module](https://github.com/fstab/grok_exporter/tree/master/tailer).
See the [FOSDEM17: Implementing 'tail -f'](https://www.youtube.com/watch?v=oc_iJXmUmrA) presentation for how go-tailer works.
# Usage
## Basic Usage: File Tailer
Here's a basic example of how to use this library to tail log files.
```go
path := "/var/log/messages" // a single file
path := "/usr/local/myapp/logs/" // a directory
path = "C:\\Program Files\\MyApp\\logs\\*.log" // or a file wildcard
// parse the path glob
parsedGlob, err := glob.Parse(path)
if err != nil {
panic(fmt.Sprintf("%q: failed to parse glob: %q", parsedGlob, err))
}
// startup a logrus logger
logger := logrus.New()
// startup the file tailer. RunFileTailer can take many path globs
tailer, err := fswatcher.RunFileTailer([]glob.Glob{parsedGlob}, false, true, logger)
// listen to the go channel for captured lines and do something with them
for line := range tailer.Lines() {
// line.Line contains the line contents
// line.File contains the name of the file that the line was grabbed from
DoSomethingWithLine(line.File, line.Line)
}
```
## Polling Tailer
We recommend using the [RunFileTailer](https://github.com/jdrews/go-tailer/blob/6f5ab8f01f5db115fcb1bd72fdea19205a364910/fswatcher/fswatcher.go#L98), which listens for file system events to trigger tailing actions. But if that isn't working for you, you can fall back to a polling listener to periodically read the file for any new log lines.
```go
// specify how often you want the tailer to check for updates
pollInterval := time.Duration(500 * time.Millisecond)
// startup the polling file tailer
tailer, err := fswatcher.RunPollingFileTailer([]glob.Glob{parsedGlob}, false, true, pollInterval, logger)
// listen to the go channel for captured lines and do something with them
for line := range tailer.Lines() {
DoSomethingWithLine(line.File, line.Line)
}
```
## Other Tailers
Along with reading from files, go-tailer can read from other sources as well.
* Tail stdin (console/shell/standard input): [RunStdinTailer](https://github.com/jdrews/go-tailer/blob/main/stdinTailer.go)
* Tail a Kafka stream: [RunKafkaTailer](https://github.com/jdrews/go-tailer/blob/main/kafkaTailer.go)
* Tail a webhook: [WebhookTailer](https://github.com/jdrews/go-tailer/blob/main/webhookTailer.go)
# Frequently Asked Questions (FAQ)
### Why was the tailer module forked from [fstab/grok_exporter](https://github.com/fstab/grok_exporter) and moved here?
grok_exporter had not been updated for 3-4 years and seems to be abandoned by [@fstab](https://github.com/fstab). It also was suffering [from quite a few security issues (CVEs) ](https://deps.dev/go/github.com%2Ffstab%2Fgrok_exporter/v0.2.8), which I've fixed. Additionally, the tailer module was not well known, had poor documentation, and I thought a separate repo would shed some well deserved light on it.
I'd welcome making upstream patches to [fstab/grok_exporter](https://github.com/fstab/grok_exporter) if/when it becomes active again!