[SOLVED] Downloading and replacing file only if target is newer than source

Issue

This is what I'm trying to achieve:

User uploads file1.jpg to Server A

Using wget Server B only downloads file1.jpg from Server A if the file is newer than the one that already exists on Server B and then replaces the file on Server B with the new one.

I know I can use:

 wget -N http://www.mywebsite.com/files/file1.jpg

To check that the target file is newer than the source but I'm a little confused as to how I format the command to let it know what and where the actual source file is?

Is it something like:

 wget -N http://www.mywebsite.com/files/file1.jpg /serverb/files/file1.jpg

Solution

You can use -P option to specify the directory where the file(s) will be downloaded:

$ wget -N -P /serverb/files/ http://www.mywebsite.com/files/file1.jpg

You are also talking about downloading and replacing the file. Be aware, that wget overwrites the file, so it is "broken" while being downloaded. I don't think you can do atomic replacement of the file using only wget. You need a small script that uses temporary files and move to atomically replace the file in Server B.

Answered By - Erki Aring

Answer Checked By - Terry (WPSolving Volunteer)