wait child process but get error: 'pid is not a child of this shell'

Question

I write a script to get data from HDFS parrallel，then I wait these child processes in a for loop, but sometimes it returns \"pid is not a child of this shell\". sometimes, i

Answer 1

Either your while loop or the for loop runs in a subshell, which is why you cannot await a child of the (parent, outer) shell.

Edit this might happen if the while loop or for loop is actually

(a) in a {...} block (b) participating in a piper (e.g. for....done|somepipe)