Top 10 Example of lsof commands in Linux and UNIX

In a Linux or UNIX operating system, there are many processes running simultaneously. These processes use files, sockets, and other resources that are managed by the operating system. To get information about these resources, we can use the "lsof" (list open files) command. Lsof is a powerful tool that can help us understand the system's state, monitor and debug applications, and troubleshoot issues. In this article, we will look at ten examples of using the lsof command in Linux and UNIX.

List all open files:

To list all the open files in the system, we can simply run the lsof command without any arguments. This will give us a comprehensive list of all the files and their corresponding processes.

lsof

List all open files for a specific user:

To list all the open files for a specific user, we can use the "-u" option followed by the username. This will give us a list of all the files opened by that particular user.

lsof -u username

List all open network connections:

To list all the open network connections, we can use the "-i" option. This will give us a list of all the network sockets and their corresponding processes.

lsof -i

List all open files for a specific process:

To list all the open files for a specific process, we can use the "-p" option followed by the process ID (PID). This will give us a list of all the files opened by that particular process.

lsof -p PID

List all open files for a specific directory:

To list all the open files for a specific directory, we can use the "+D" option followed by the directory path. This will give us a list of all the files opened by processes running in that directory.

lsof +D /path/to/directory

List all open files for a specific file:

To list all the open files for a specific file, we can use the "+f" option followed by the file path. This will give us a list of all the processes that have the file open.

lsof +f /path/to/file

List all open files for a specific TCP port:

To list all the open files for a specific TCP port, we can use the "-i" option followed by the TCP port number. This will give us a list of all the processes that are listening on that particular port.

lsof -i TCP:port_number

List all open files for a specific UDP port:

To list all the open files for a specific UDP port, we can use the "-i" option followed by the UDP port number. This will give us a list of all the processes that are listening on that particular port.

lsof -i UDP:port_number

List all open files for a specific NFS file system:

To list all the open files for a specific NFS file system, we can use the "-N" option followed by the NFS file system name. This will give us a list of all the files opened by processes that are using that particular NFS file system.

lsof -N nfs_file_system_name

List all open files for a specific user and process:

To list all the open files for a specific user and process, we can combine the "-u" and "-p" options. This will give us a list of all the files opened by that particular user and process.

lsof -u username -p PID

In this article, we have seen ten examples of using the lsof command in Linux and UNIX. Lsof is a powerful tool that can help us understand the system's state, monitor and debug applications, and troubleshoot issues. By using the various options provided by the lsof command, we can get detailed information about the files, sockets, and other resources used by processes running in the system. This information can be very useful in identifying and resolving issues related to file access, network connectivity, and other system resources.