see-files-opened-by-process.md

See list of files opened by a process

To see a list of files currently open by processes, you can use the lsof command. Pair with a flag or grep for more power.

Examples

See all the files Firefox has open:

lsof | grep firefox

See processes using a file on a specific port number with the -i flag:

lsof -i :3000 

Results are formmated like this:

COMMAND   PID          USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
node    16150 christianwood   13u  IPv6 0x7cbe288dc6d3a25f      0t0  TCP *:hbci (LISTEN)

See the man page for full list of options.

Using lsof to troubleshoot port conflicts in local development

Say you want to spin up a local development server, but you receive an error that the port you want to use is already in use.

With node, the error might look like this for a develpment server running on port 3000: Error: listen EADDRINUSE :::3000.

Track down what process is using that port with lsof:

lsof -i :3000

Get the ID of the offending process:

COMMAND   PID          USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
node    16150 christianwood   13u  IPv6 0x7cbe288dc6d3a25f      0t0  TCP *:hbci (LISTEN)

Kill that process to free up the port:

kill 16150