Question

I want to check a specific directory in linux bash every 2 second and if any file exists there make a copy of that file to a directory before a running daemon process hijacks that file (make some processing and modification on that file and quickly move the processed file to another directory).

I tried this:

while true; do
  cp * /home/a/*;
  sleep 1;
done

But it does not work: I guess my cp syntax must be wrong. I tried /home/a/*, /home/a and /home/a/ but none of them worked.

Is there any way I can do this in bash shell?

Answer 1

You’re nearly there, but you need to account for the case where you have no files in that directory.

With the right options in bash, it’s fairly easy:

#! /bin/bash

shopt -s nullglob # to get an empty list if no file is present

while true ; do
    for i in * ; do
        echo "Intercepted $i"
        cp "$i" /home/a/
    done
    sleep 1
done

(Note that this is pretty unreliable in general. You could copy partially written-to files, miss files completely, etc.)