Script to monitor folder for new files?

Question

How do I detect new files in a folder with a bash script? I would like to process the files as soon as they are created in the folder. Is this possible to do so or do I have to schedule a script with cron that that check for new files each minute or so?

Answer 1

You should consider using inotifywait, as an example:

inotifywait -m /path 2>&- | awk '$2 == "CREATE" { print $3; fflush() }' |
    while read file; do
        echo "$file"
        # do something with the file
    done

In Ubuntu inotifywait is provided by the inotify-tools package.

Answer 2

I prefer incron, as its easier to manage. Essentially its a service that leverages inotify and you can setup configurations to take action based on file change operations.

Ex:

<directory> <file change mask> <command or action>  options
/var/www/html IN_CREATE /root/scripts/backup.sh

You can see a full example here: http://www.cyberciti.biz/faq/linux-inotify-examples-to-replicate-directories/

Answer 3

Bash cannot do this easily. You'd have to basically get a list of all the files in the folder and periodically get a new list and compare them to see whats changed.

What you're looking for is called inotify. Its built into the linux kernel and you can basically sit there waiting for something to happen at which point inotify comes back and says 'hey, theres a new file called foobar'

To accomplish what you want you'd have to switch to something like perl and use Linux::Inotify2 (python probably supports inotify as well, but I'm a perl person).

Answer 4

I am assuming the target folder (I'll call it isempty just for convenience) is empty and you are waiting for one or more files to be dropped there.

You can use the following command:

ls -1A isempty | wc -l

just to check if the folder is still empty, in fact it will return a 0 if there is no new file (hence the isempty folder is still empty) or, on the other hand, it will return a value greater than 0 (actually the number of files currently in the folder).

That said a silly if/then test can make the rest of the work:

if [ $(ls -1A isempty | wc -l) -gt 0 ] ; then do_something ; fi

Of course the do_something function will have to manipulate the file(s) within the isempty folder and then remove it(them) from the folder itself after processing.

Adding a line like the following in your crontab will run the check once a minute and will trigger the do_something action if the folder is not empty of course:

* * * * *     if [ $(ls -1A isempty | wc -l) -gt 0 ] ; then do_something ; fi

Answer 5

Check out the script mentioned in this url . It uses inotifywait to recursively monitor and record file creation events.