portcop 🚔

Your cross-platform port detective — find, inspect, and kill processes by port number.

No dependencies. Works on macOS, Linux, and Windows.

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Why

Every fullstack developer has googled lsof -i :3000 at least once a week. portcop makes it one clean command that works everywhere — no memorizing OS-specific flags, no piping through grep, no copy-pasting PIDs.

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Install

npm install -g portcop

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Usage

Check what's on a port

portcop 3000

  Checking port 3000...

  ✘ Port 3000 is occupied

    Process : node
    PID     : 8421
    Command : node server.js

  Kill it? (y/n)

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Kill immediately without prompt

portcop 3000 --kill

  ✔ Killed node (PID 8421)

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Check if a port is free

portcop free 3000

  ✔ Port 3000 is free

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Find first free port in a range

portcop free 3000-3010

  Scanning ports 3000–3010...
  ✔ First free port: 3003

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How it works

macOS: uses lsof

Linux: tries 3 strategies in order, using the first one that works:

1. lsof — available on most distros
2. ss — modern replacement for netstat, used when lsof isn't installed
3. /proc/net/tcp — pure Linux kernel file, no tools needed at all. Works in Docker containers, CI runners, and minimal environments where nothing is installed

Windows: chains netstat -ano → tasklist (no single command gives port + process name together)

OS	Kill
macOS / Linux	kill -9 PID
Windows	taskkill /PID /F

All OS differences are abstracted away. The CLI output is identical everywhere.

Note: On some systems, killing processes on privileged ports (< 1024) may require sudo.

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Options

Flag	Alias	Description
--kill	-k	Kill without confirmation prompt
--help	-h	Show help

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License

MIT