How to redirect file output to a different directory?

Question

I have a program that regularly outputs files to a directory, let's say /a/b. I am utterly unable to change where these files are outputted. But for me to use them, I must first move them to, let's say, /c/d, an already existing directory. I'm growing tired of regularly moving over the file contents, so is there some way to redirect everything written in that directory to another? I've already tried ln -s but with my limited knowledge of the linking command I couldn't accomplish anything. Changing any code of the program is not possible. Thanks for the help.

Answer 1

short of being able to delete /a/b directory, your ln -s command will not give you anything.

but if you can find a few seconds that nothing is writing to this /a/b directory, you can do this :

cd /a
rm -r b   # make sure you have a backup of the contents of this directory 
ln -s /c/d b

now any application who will write into /a/b, will be directed to write these files into /c/d, provided they have write rights.

Answer 2

Here:

while :; do cp /a/b/* /c/d/; sleep 60; done

It copies the entire content of /a/b/ to /c/d/ every 60 seconds.

It does have a drawback: If the files are big (more than a few GB?) then copying might take a while. If this is a problem, comment and I'll implement something optimised for big files (with tail -f) which will also redirect the content in real time