Journalctl

This is a module for accessing systemd journal.

API

You can find the documentation page here

Require the module and create a new instance:

const Journalctl = require('@bryopsida/journalctl')
const journalctl = new Journalctl([opts])

The optional object opts can have the following properties:

• identifier: Just output logs of the given syslog identifier (cf. man journalctl, option '-t')
• unit: Just output logs originated from the given unit file (cf. man journalctl, option '-u')
• filter: An array of matches to filter by (cf. man journalctl, matches)
• all: Show all fields in full, even if they include unprintable characters or are very long. (cf. man journalctl, option '-a')
• lines: Show the most recent journal events and limit the number of events shown (cf. man journalctl, option '-n')
• since: Start showing entries on or newer than the specified date (cf. man journalctl, option '-S')

Event: 'json-message'

journalctl.on('json-message', event => {})

Is fired on every decoded json message.

Event: 'raw-message'

journalctl.on('raw-message', buffer => {})

Is fired on every data event from the journalctl sub process.

Event: 'error'

journalctl.on('error', err => {})

Is fired whenever the journalctl sub process emits an error or the class encounters an error condition.

Event: 'close'

journalctl.on('close', () => {})

Is fired whenever the journalctl sub process exits with status code 0.

Method: stop

journalctl.stop([callback])

Method: getStdout

journalctl.getStdout().pipe(process.stdout)

Returns the stdout stream from the journalctl sub process.

Method: getStderr

journalctl.getStderr().pipe(process.stderr)

Returns the stderr stream from the journalctl sub process.

Examples

Decode and tail all logs

const Journalctl = require('@bryopsida/journalctl')

const logger = new Journalctl().on('json-message', e => {
  console.log(e)
})

process.on('SIGINT', () => {
  logger.stop(() => {
    process.exit()
  })
})

Pipe raw output

const Journalctl = require('@bryopsida/journalctl')

const j = new Journalctl({
  disableJSONMessages: true,
  emitRawMessages: false
})

j.getStdout().pipe(process.stdout)
j.getStderr().pipe(process.stderr)

process.on('SIGINT', () => {
  j.stop(() => {
    process.exit()
  })
})

Process raw events

const Journalctl = require('@bryopsida/journalctl')

const j = new Journalctl({
  disableJSONMessages: true,
  emitRawMessages: true
}).on('raw-message', buffer => {
  process.stdout.write(buffer)
})

process.on('SIGINT', () => {
  j.stop(() => {
    process.exit()
  })
})

Use command prefix

const Journalctl = require('@bryopsida/journalctl')

const j = new Journalctl({
  commandPrefix: ['vagrant', 'ssh', '-c'],
  quoteArgs: true,
  spawnOptions: {
    shell: true
  }
}).on('json-message', e => {
  console.log(e)
})

process.on('SIGINT', () => {
  j.stop(() => {
    process.exit()
  })
})

Test Environment

If you need a test environment with journald running, and you have vagrant installed, you can spin one up with vagrant up and remove it with vagrant destroy once you are finished.

You can access the environment by using vagrant ssh. This project is available at /vagrant inside the vagrant box.