Matttermost, Inc.

Mattermost Recipe: Notify Mattermost when a file is uploaded

Mattermost Recipe: Notify Mattermost when a directory is changed

Problem

You’re waiting for a file to be uploaded to your server, but don’t want to keep refreshing your FTP client

Solution

1. Install inotify-tools

inotify-tools is a package available for most Unix systems that includes inotifywatch and inotifywait utilities. To install:

CentOS/Red Hat:

sudo yum install inotify-tools

Ubuntu/Debian:

sudo apt-get install inotify tools

2. Create an incoming webhook in Mattermost

Instructions are available in our docs.

3. Write a script

Here’s a simple script that will watch a directory and send a request to the Webhook.

#!/bin/bash
  
webhook_url="https://chat.example.com/hooks/dk3xou5fh7ham7xhhezjtr5hxj"

if [[ -d $1 ]]; then
    watch_path=$1
else
    echo "$1 must be a directory"
    exit 1
fi

inotifywait -q -m $watch_path -e create -e moved_to |
    while read path action file; do
        message_text="The file $file appeared in directory $path via $action"
        curl --silent --output /dev/null -i -X POST -H 'Content-Type: application/json' -d "{\"text\": \"$message_text\"}" $webhook_url
    done

To run it, copy it to a file, e.g. watch-directory.sh, make it executable with chmod +x and then run it like this:

$ ./watch-directory.sh ~/test

Then, in another terminal, cd to the directory you’re watching, and run this command:

$ touch a_file.txt
$ cp ~/src.txt test
$ mv ~/main.rb test/

When you do that, you should see these messages posted to Mattermost:

Discussion

inotifywait uses Linux’s inotify API, which provides system monitoring information. This API has been ported to numerous programming languages including Go so it’s possible to make a Mattermost plugin using it.

inotifywait can monitor several different kinds of file events. For example, checking for the CLOSE_WRITE event will let you know when a file has been changed. This could be used to monitor configuration files for changes. The UNMOUNT event, which is triggered when the remote filesystem is unmounted, which could notify you if a fileserver goes down.

Because inotify has an API there are a lot of other solutions. In my first recipe I used incrontab to monitor a directory to trigger video processing. But if you need to quickly monitor a directory from a terminal inotifywait is the way to go.

Feedback appreciated!

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