Capture pid when starting a background process in bash

Question

I'm trying to capture the pid of a background process run in bash.

I tried

somecommand & > somecommand.pid

It outputs the pid to the screen but it's not part of stdout of the command.

[1] 1778

Answer 1

The special variable $! contains the PID of the most recent job placed in the background:

$ sleep 4 &
$ sleep_pid=$!
$ echo $sleep_pid
4456

This is documented in Special Parameters of man bash