yitz 1207111767 learn Expands to the process ID of the most recently executed background (asynchronous) command.
yitz 1207111791 forget
yitz 1207111794 learn $! expands to the process ID of the most recently executed background (asynchronous) command.
greycat 1540832519 forget
greycat 1540832520 learn $! expands to the process ID of the most recently executed background (asynchronous) command. In bash 4.4 and later this includes process substitutions.