lsof

CLI

List open files and the processes that opened them.

Find which process has a file or port open

4 of 4 recipes verified by execution · 2026-09-17#files #processes #network #sockets

Verified commands

Executed by our harness on the platforms shown; the assertion checked the actual result, not just the exit code.

Find the process listening on a port

Verified macOS · Linux · 2026-09-17

lsof -nP -iTCP:3000 -sTCP:LISTEN

Common failures (1)

no outputnothing is listening on that port, or the process belongs to another user: retry with sudo

Fallbackss -ltnp 'sport = :3000'

Kill the process listening on a port

Verified macOS · Linux · 2026-09-17

kill $(lsof -t -iTCP:3000 -sTCP:LISTEN)

Common failures (1)

Fallbackfuser -k 3000/tcp

Find the process listening on a port (Linux, no lsof)

Linux only

Verified Linux · 2026-09-17

ss -ltnp 'sport = :3000'

Kill the process on a port (Linux, no lsof)

Linux only

Verified Linux · 2026-09-17

fuser -k 3000/tcp

Homebrewbrew install lsof

aptsudo apt install lsof

When to use: Debugging 'port in use' errors or finding processes holding files
Quick examples: lsof -i :3000 # what's using port 3000
lsof -p 1234 # files opened by PID
lsof /var/log/app.log # who has this file open

curl -s https://clihub.com/api/tools/lsof | jq '.agentHints.provenRecipes[] | {task, command, verified}'

Or call get_tool with slug lsof on the MCP server at https://clihub.com/mcp.