What is the use of lsof command (List Open Files) ?

lsof = List Open Files

Lists files (pipes, sockets, directories, devices, etc.) information that are opened by various processes. 

This information contains :

•  FD : File descriptor 
• cwd : Current working directory
• txt : Text file
• mem : Memory mapped file
• mmap : Memory mapped device
• NUMBER : Actual file descriptor

• TYPE : File type
• REG : Regular File
• DIR : Directory
• FIFO : First In First Out
• CHR : Character special file

• NAME : File name
• PID : Process ID

Examples

List all opened files belongs to all active processes

# lsof

List processes which opened a specific file

# lsof /opt/application/myapp/logs/myapp.log

# lsof /var/log/syslog

List processes which is using a mount point

# lsof /home

List opened files under a dir

# lsof +D /var/log/

List files opened by specific user

# lsof -u shaan

List files opened by specific process

# lsof -p 1753

List processes listening on a specific port

# lsof -i :25