shell - monitor for file then copy to another directory


I'm relatively new to unix scripting, so apologies for the newbie question.

I need to create a script which will permanently run in the background, and monitor for a file to arrive in an FTP landing directory, then copy it to a different directory, and lastly remove the file from the original directory.

The script is running on a Ubuntu box.

The landing directory is /home/vpntest

The file needs to be copied as /etc/ppp/chap-secrets

So far, I've got this

if [ -f vvpn_azure.txt ]; then
cp vvpn_azure.txt /etc/ppp/chap-secrets
rm vvpn_azure.txt

I can run this as root, and it works, but only as a one off (I need it to run permanently in the background, and trigger each time a new file is received in the landing zone.)

If I don't run as root, I get issues with permissions (even if I run it from within the directory /home/vpntest.)

Any help would be much appreciated.

1 Answer: 

Updated: crontab correction and extra info

One way to have a check and move process in background with root permissions, is the "polling" approach done via root user's crontab, with your script.


  1. Revise your /home/vpntest/


if [ -f "$new_file" ]; then
    mv $new_file /etc/ppp/chap-secrets
  1. Log out. Log in as root user.

  2. Add a cron task to run the script:

    crontab -e

If this is a new machine, and your first time running crontab, you may get a prompt first to choose an editor for crontab, just choose and continue into the editor.

The format is m h dom mon dow command, so if checking every 5 minutes is sufficiently frequent, do:

*/5 * * * * /home/vpntest/
  1. Save and close to apply.

It will now automatically run the script every 5 minutes in the background, helping you to move the file if found.


Root user, because you mentioned it only worked for you as root.

So we set this in the root user's crontab to have sufficient permissions.

man 5 crontab informs us:

Steps are also permitted after an asterisk, so if you want to say 'every two hours', just use '*/2'.

Thus we write */5 in the first column, which is the minutes column, to set for "every 5 minutes".

  • uses absolute paths, can run from anywhere
  • re-arranged so one variable new_file can be re-used
  • good practice to enclose any values being checked within your [ ] test
  • uses mv to write over the destination while removing itself from the source directory

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