filemon

filemon is a program for monitoring one or more files or directories for the IN_CLOSE_WRITE event;

for every event that is notified by the operating system, filemon invokes a command on it.

Usage

filemon requires at least one -d parameter and one -c parameter:

one or more -d file_or_directory parameter; each -d parameter requires the name of a file or directory to watch for events.
a single -c command parameter which specifies the command to invoke when an event on the files/directories.

Whenever an event is notified to filemon, the command is invoked, the absolute file name is concatenated to the command.

Example

example:

filemon -d /tmp/ -c "ls -l"

with this command, filemon monitors directory /tmp/; when a IN_CLOSE_WRITE event is notified (for example: after a file is created and closed in the /tmp/ directory), the command "ls -l" is executed with the file as parameter

output running the example, and running the command touch /tmp/this_is_a_new_file in a separate console:

$ filemon -d /tmp/ -c "ls -l"
filemon[9714]: command: ls -l
filemon[9714]: number of specified files/directories: 1
filemon[9714]: directory[0]: /tmp/
filemon[9714]: watching /tmp
filemon[9714]: ready!
filemon[9714]: read 192 bytes from inotify fd
filemon[9714]: show_inotify_event [dir_name='/tmp' wd= 1] 
filemon[9714]: show_inotify_event file name = this_is_a_new_file 
filemon[9714]: mask = IN_CREATE 
filemon[9714]: show_inotify_event [dir_name='/tmp' wd= 1] 
filemon[9714]: show_inotify_event file name = this_is_a_new_file 
filemon[9714]: mask = IN_OPEN 
filemon[9714]: show_inotify_event [dir_name='/tmp' wd= 1] 
filemon[9714]: show_inotify_event file name = this_is_a_new_file 
filemon[9714]: mask = IN_ATTRIB 
filemon[9714]: show_inotify_event [dir_name='/tmp' wd= 1] 
filemon[9714]: show_inotify_event file name = this_is_a_new_file 
filemon[9714]: mask = IN_CLOSE_WRITE 
filemon[9714]: cmd: ls -l /tmp/this_is_a_new_file
filemon[9978]: [child process] pid=9978
-rw-r--r-- 1 marco marco 0 Aug 10 11:50 /tmp/this_is_a_new_file
filemon[9714]: [parent] child process has terminated, returning: 0

Setup

build on linux:

gcc filemon.c -o filemon -s

install to /usr/bin/ directory:

sudo cp filemon /usr/bin/

Development

filemon is developed using Eclipse IDE for C/C++ Developers. The repository contains all project files.

Run as a systemd service

filemon can be run as a systemd service.

Here is a sample service configuration file:

[Unit]
Description=filemon service

[Service]
User=marco
Group=marco
ExecStart=/usr/bin/filemon -d /home/marco/directory/ -c /home/marco/process_file.sh

[Install]
WantedBy=multi-user.target

In this example, filemon monitors the /home/marco/directory/ directory; when the IN_CLOSE_WRITE event regarding a file in the directory is notified to filemon, it invokes the /home/marco/process_file.sh command on the file which is passed as a parameter to the command.

Limitations

filemon is being used and tested on Debian 11/12 and Ubuntu 20/22 operating systems.

marcotessarotto / filemon