lsof

lsof, short for “list open files”, is used to list detailed information about files that are currently opened by processes.

Basic Syntax

lsof [options] [files or directories]

• options: This specifies the options for the command.
• files or directories: This specifies the files or directories for which to display open files.

Commonly Used Options

• -i: This shows information about files opened by Internet connections.
• -u: This shows information about files opened by a specific user.
• -p: This shows information about files opened by a specific process ID.
• -c: This shows information about files opened by a specific command name.
• -t: This shows only the process IDs of files being used.
• -n: This prevents the conversion of network numbers to hostnames.
• -F: This formats the output of the command.
• -X: This shows more verbose output.

Useful Examples

• lsof /var/log/messages: This displays the processes that have opened the /var/log/messages file.
• lsof -i :80: This displays the processes that are using the port 80.
• lsof -u user1: This displays the files that are opened by the user1 user.
• lsof -c sshd: This displays the files that are opened by the sshd command.
• lsof -p 1234: This displays the files that are opened by the process with ID 1234.
• lsof -i [email protected]:22: This displays the processes that are using the 22 port for the IP address 192.168.1.10.
• lsof -i udp:53: This displays the processes that are using the 53 port for UDP connections.