Writing the output of a process to a file which has the process id in its file name

Question

This is what I'm trying to achieve:

• Run a command/process in background and have it's output redirected to a temporary file which is named after the process id of the background process.
• Example:
  • top & // process Id of this background process is 1123
  • The output of top should be stored in a file 1123.temp

Is this possible? Because to truly run it in the background wouldn't we have to do the redirection before marking it as a background process? Or is there some technique to work around this?

Answer 1

You can redirect to a temporary file and then mv that file to the required name e.g.

process > /tmp/process.log &
mv /tmp/process.log /tmp/$!.log

$! is the pid of the previously backgrounded process. Note that the mv simply renames that file. It won't interrupt writing to it.