Inotifywait – Watch Directory for Specific File Extensions

filesystemsinotifymonitoringshellshell-script

You should consider using inotifywait, as an example:

inotifywait -m /path -e create -e moved_to |
    while read path action file; do
        echo "The file '$file' appeared in directory '$path' via '$action'"
        # do something with the file
    done

My question is that, the above script watches a directory for creation of files of any type, but how do I modify the inotifywait command to report only when a file of certain type/extension is created (or moved into the directory) – e.g. it should report when any .xml file is created.

WHAT I TRIED:

I have run the inotifywait --help command, and have read the command line options. It has --exclude <pattern> and --excludei <pattern> commands to EXCLUDE files of certain types (by using regEx), but I need a way to INCLUDE just the files of a certain type/extension.

Best Answer

how do I modify the inotifywait command to report only when a file of certain type/extension is created

Please note that this is untested code since I don't have access to inotify right now. But something akin to this ought to work:

inotifywait -m /path -e create -e moved_to |
    while read path action file; do
        if [[ "$file" =~ .*xml$ ]]; then # Does the file end with .xml?
            echo "xml file" # If so, do your thing here!
        fi
    done

Related Solutions

How does inotify work

Inotify is an internal kernel facility. There is no “inotify file”. There are dedicated system calls inotify_init, inotify_add_watch and inotify_rm_watch that allow processes to register themselves to be notified when certain filesystem events happen. When the event happens, the process receives a description of the event through the file descriptor returned by inotify_init.

The OS isn't “told” that a file has been changed: it knows, because it's doing the changing. It's the application that's told that a file has been changed instead of having to go looking.

The program inotifywait provides a simple way to use inotify from the command line.

Shell – ny way to use xargs across a pipe

If I understand correctly, you want to fire up one instance flac … | lame … for each input line, and interpolate the input into the arguments to both commands.

Since you need xargs to start a pipeline, you need to make it start a program that's capable of creating pipelines, i.e. a shell.

inotifywait -m -r -q -e moved_to --format "%w%f" ~/test |
xargs -l sh -c 'flac -cd "$0" - | lame -b 320 - "/media/1tb/$0.mp3"'

Alternatively, have the calling shell read lines one by one and run the pipeline.

inotifywait -m -r -q -e moved_to --format "%w%f" ~/test |
while IFS= read -r file; do
  flac -cd "$file" - | lame -b 320 - "/media/1tb/$file.mp3"
done

Note that the format %w%f produces an absolute path, to which you're prepending /media/1tb and appending .mp3. If you want to strip off the directory part of the file in the lame command, change $file to ${file##*/}. If you want to strip off the extension, change $file to ${file%.*}. If you want to do both, you'll have to do it in two steps. If you want to reproduce the directory hierarchy under /media/1tb, you can use mkdir -p.

cd ~/test
inotifywait -m -r -q -e moved_to --format "%w%f" . |
while IFS= read -r file; do
  [ -f "$file" ] || continue; # skip directories and other special files
  dir=${file%/*}; file=${file##*/}
  mkdir -p "/media/1tb/$dir"
  flac -cd "$dir/$file" - | lame -b 320 - "/media/1tb/$dir/${file#.*}.mp3"
done

Best Answer

Related Solutions

How does inotify work

Shell – ny way to use xargs across a pipe

Related Question