fuser

fuser(1) - Linux man page

wikipedia fuser (Unix)

The Unix command fuser is used to show which processes are using a specified computer file, file system, or Unix socket.

Example

Find Which Process Accessing a Directory

$ fuser .
OR
$ fuser /home/tecmint

Under the ACCESS column, you will see access types signified by the following letters:

1. c – current directory
2. e – an executable file being run
3. f – open file, however, f is left out in the output
4. F – open file for writing, F is as well excluded from the output
5. r – root directory
6. m – mmap’ed file or shared library

Find Which Process Accessing A File System

Next, you can determine which processes are accessing your ~.bashrc file like so:

$ fuser -v -m .bashrc

The option, -m NAME or --mount NAME means name all processes accessing the file NAME. In case you a spell out directory as NAME, it is spontaneously changed to NAME/, to use any file system that is possibly mounted on that directory.

How to Kill and Signal Processes Using fuser

In this section we shall work through using fuser to kill and send signals to processes.

In order to kill a processes accessing a file or socket, employ the -k or --kill option like so:

$ sudo fuser -k .

To interactively kill a process, where you are that asked to confirm your intention to kill the processes accessing a file or socket, make use of -i or --interactive option:

$ sudo fuser -ki .

The two previous commands will kill all processes accessing your current directory, the default signal sent to the processes is SIGKILL, except when -SIGNAL is used.

Suggested Read: A Guide to Kill, Pkill and Killall Commands in Linux

You can list all the signals using the -l or --list-signals options as below:

$ sudo fuser --list-signals 

List All Kill Process Signals

Therefore, you can send a signal to processes as in the next command, where SIGNAL is any of the signals listed in the output above.

$ sudo fuser -k -SIGNAL

For example, this command below sends the HUP signal to all processes that have your /boot directory open.

$ sudo fuser -k -HUP /boot 

Try to read through the fuser man page for advanced usage options, additional and more detailed information.

That is it for now, you can reach us by means of the feedback section below for any assistance that you possibly need or suggestions you wish to make.

Check Processes Using TCP/UDP Sockets

Using fuser we can also check the processes using TCP/UDP sockets. Since the above stated socket_serv sample C program executable is running on TCP port 5000, lets use fuser utility on this socket.

$ fuser -v -n tcp 5000
                       USER        PID ACCESS COMMAND
5000/tcp:            himanshu   4334   F....  socket_serv

So we see that fuser gives all detailed information of the process running on TCP port 5000.

Other than the examples above, we can use the ‘-m’ flag with this utility to display processes using a mounted file system like a USB drive.