logger-filter

Interactive log filter for any CLI process. Wrap any command and filter its output in real time — no restarts needed.

Zero dependencies. Node.js only.

Install

npm install -g logger-filter

Or clone and link locally:

git clone https://github.com/caioeliasss/logger-filter.git
cd logger-filter
npm link

Usage

filter <command> [args]

Examples:

filter node server.js
filter npx nodemon server.js
filter python main.py
filter --env production npm start
filter --cwd /path/to/project node app.js

Flags:

Flag	Description
--env <value>	Set NODE_ENV (default: development)
--cwd <path>	Working directory for the child process
--track	Inject source filename into every log line (Node.js only)
--no-track	Disable auto-track even for Node.js commands

Auto-track: --track is enabled automatically when the command is node, nodemon, npx, ts-node, tsx, or bun. Use --no-track to opt out.

Project Config

Run filter init in your project directory to create a .filter.json config:

filter init

This creates .filter.json with your runner and environment. After that, running filter with no arguments uses the config:

{
  "run": "npx nodemon server.js",
  "env": "development"
}

Interactive Commands

Type while the process is running and press Enter:

Command	Description
+pattern	Show only lines matching pattern
-pattern	Hide lines matching pattern
!pattern [--color]	Highlight matching lines
/remove <text>	Remove a specific filter by pattern text
/reset	Remove all filters and highlights
/clear	Clear screen and reprint history
/list	List all active filters
/track	Toggle source filename display
/help	Show command reference
Ctrl+C	Kill process and exit

Highlight colors: yellow (default), red, green, blue, magenta, cyan, white

Demo

Start any process and filter its output without restarting:

$ filter node server.js

Server listening on port 3000
GET /api/users 200 12ms
GET /healthcheck 200 1ms
GET /api/orders 200 34ms
GET /healthcheck 200 1ms
POST /api/users 201 88ms

[filter] > -healthcheck
[filter] hide: "healthcheck" (total: 1)

GET /api/products 200 22ms
POST /api/orders 201 55ms
GET /api/users 200 11ms

Highlight errors in red with !error --red:

  [filter] > !error --red
  [filter] highlight: "error" (red)

  GET /api/users 200 14ms
- ERROR Failed to connect to database: timeout after 5000ms
- ERROR Retrying connection (1/3)...
  GET /api/products 200 22ms
- ERROR Retrying connection (2/3)...
  POST /api/orders 201 55ms

Remove a specific filter or reset everything:

[filter] > /remove healthcheck
[filter] removed filter: "healthcheck"

[filter] > /reset
[filter] all filters and highlights removed

Track Mode

Start with --track to inject source filenames into every log line. Works with any Node.js process. Enabled automatically for node, nodemon, npx, ts-node, tsx, and bun.

filter --track node app.js

Each console.log call is prefixed with the file it came from, rendered in italic:

main.js - Server listening on port 3000
routes/users.js - GET /api/users 200 12ms
middleware/auth.js - Token verified for user 42
routes/users.js - GET /api/users 200 11ms

Toggle the filename display at runtime with /track — history reprints with or without filenames.

Since filenames appear in the output, you can filter by source file:

[filter] > -middleware/auth.js
[filter] hide: "middleware/auth.js" (total: 1)

main.js - Server listening on port 3000
routes/users.js - GET /api/users 200 12ms

License

MIT