Using a shell script, can I watch a folder and block program execution until a file in a certain folder changes?
After some suggestions to check out inotifywait I ended up with a solution that works for me as desired.
inotifywait --event modify,create ./targetfolder/; echo "new change, that I am interested in, occurred in targetfolder";It turned out I was interested in both file modification and file creation events.
There is inotifywait which seems to do the job, The Wiki
As another commenter said, you want inotifywait:
The simplest solution is entr, I use it a lot for development - https://www.linuxbash.sh/post/entr-rerun-commands-when-files-change
What is the end goal?
a hobby project: generate a rss feed based on recent file changes in a directory. But I thought this can also have many applications …
- auto formatting code files on change
- automatic backups of a certain folder: run rsync on change in folder.
Are you familiar with CI/CD pipelines? You could use Git along with a service like Woodpecker CI or Gitlab Runners.
Maybe inotify or one of those “watcher” (not “watch”) tools available, but I don’t remember which one to use.
Can continuously loop over the file, examine the md5 hash for changes.
Run the script if it has changed.
https://stackoverflow.com/questions/6475252/bash-script-watch-folder-execute-command
daemon() { chsum1="" while [[ true ]] do chsum2=`find src/ -type f -exec md5 {} \;` if [[ $chsum1 != $chsum2 ]] ; then if [ -n "$chsum1" ]; then compile fi chsum1=$chsum2 fi sleep 2 done }Oh god please don’t do this. Constantly reading the file is just stressing your IO for no reason.
Please inotify instead:
The fuck…
Even if you wanted to implement a solution like this, which you shouldn’t, why on earth monitor the MD5 sum instead of just the mtime of the file??? Like, doing a checksum is the least efficient method of checking this possible.
Like, you could do a simple while loop with a
find myfile.txt +mmin 1; sleep 30in it. Adjust numbers to your desired tolerance.Again, don’t do that. But if you must, definitely don’t do an md5sum for godssake.
I really like this, replace compile with whatever command you desire I guess.
This is a terrible solution. You will stress your IO for no reason.
On the upside, you do not need to install the
inotifywaitpackage.md5sumalready installed on my system hahaIf you are a big fan of wasting disk performance, CPU cycles, and ultimately power.
It isn’t a terrible solution if you are checking infrequently just as ever 30 minutes.
why is that a plus
I do not need to install anything/can work on bare install without internet connection?
ah, fair.
You should be able to tie into the kernel with some C programming if you want to go extra small.
Block execution not entirely. You could chmod it as non-x and use inotifywatch to flip it back.
Edit: I misunderstood you, use inotifywait like the other person suggested.
