PID returned by spawn differs from Process.pid of the child process-CodePudding

I want to spawn a potentially long running process and save its PID so I can kill it later if needed. The problem is that the PID I get from spawn is not the same I get from Process.pid (in the child process). The result of Process.pid matches what I see running ps in the command line.

Here is the code for parent and child

parent.rb

puts "Hi parent"
pid = spawn "ruby child.rb 10 &"
puts pid
Process.detach(pid)
sleep 3
puts "Bye parent"

child.rb

puts "Start pid #{Process.pid}"
sleep ARGV.first.to_i
puts "End pid #{Process.pid}"

Output

Hi parent
1886789
Start pid 1886791
Bye parent
End pid 1886791

CodePudding user response：

Looks like the background job operator (&) is causing the intermediate process 1886789. When I remove the background job operator, I get the following output:

Hi parent
93185
Start pid 93185
Bye parent
End pid 93185