Lsof

lsof is one of the swiss army knife tools. Every Unix sysadmin should have a good working knowledge of this tool.

Examples

List files being accessed at or below a specified directory

lsof +D $DIRECTORY

List network connections

lsof -i

List files in use by a different process

lsof -p 5432

This options allows multiple comma seperated processes:

lsof -p 5432,6543,7654

And negation by the use of ^.

lsof -p ^8765