# lsof

Canonical page: https://vitalsmac.com/glossary/lsof

Activity Monitor glossary, When something goes wrong. What is lsof on a Mac?

Also: list open files

**Short answer:** lsof is a Terminal command that lists the files, folders and network connections every process has open. On a Mac it answers which process is using a file, what is keeping a disk from ejecting and what is listening on a port.

lsof stands for list open files, and it comes with macOS. Run with nothing after it, it prints thousands of lines, one per open file, so it is almost always given a file, a folder, a disk or a port to narrow the list.

Without `sudo` it shows only your own processes. With it, macOS's own are included, such as Spotlight's.

## The lsof commands worth knowing

Each one takes a path, a port or a process to narrow the list.

- `lsof /path/to/file`: what has this file open
- `sudo lsof /Volumes/NAME`: everything open on a disk
- `lsof +D /path/to/folder`: everything open inside a folder
- `lsof -nP -iTCP:3000 -sTCP:LISTEN`: what is listening on port 3000
- `lsof -p <PID>`: every file one process has open

## How to read the output

COMMAND is the process name, cut to nine letters, PID its number and USER who runs it. FD says how the file is open: a number with r for reading, w for writing or u for both, `cwd` for the folder the process works in and `txt` for the program and the libraries it loaded. NAME is the path, or the network address.

## Why lsof is slow, or prints warnings

Looking inside a large folder with `+D` reads every file under it and can take minutes. Warnings about files it cannot read are normal without sudo.

## Questions people ask

### What does lsof stand for?

List open files.

### Is lsof installed on a Mac?

Yes. It comes with macOS, at `/usr/sbin/lsof`.

### Why does lsof show nothing?

Nothing of yours has the file open. Run it with `sudo` to include the processes macOS and other users run.

## In Vitals

Vitals reads the same information and shows it without Terminal: Open Files lists every disk with the apps holding files on it, and Ports lists every listening port with the process behind it.

## Related

- [Listening port](https://vitalsmac.com/glossary/listening-port)
- [Open Files and Ports](https://vitalsmac.com/glossary/open-files-and-ports)
- [PID](https://vitalsmac.com/glossary/pid)
- [Force Quit](https://vitalsmac.com/glossary/force-quit)

Looking for something better than Activity Monitor? See [the best Activity Monitor alternatives for Mac](https://vitalsmac.com/best-activity-monitor-alternatives), or [every term in the glossary](https://vitalsmac.com/glossary).