lsof:tldr:055e0

The lsof command is used to list open files in Unix-like operating systems. It provides information about files that are currently opened by processes on the system.

The ${filename} part in the command is a placeholder for the actual name of the file you want to examine. You need to replace ${filename} with the actual file name or path you want to check.

For example, if you want to see which processes have the file "example.txt" open, you would run:

lsof example.txt

The output of the command will show you the details of the processes that have the file open, such as the process ID (PID), user, file descriptor, and the type of access (read, write, etc.).