Background running program method

(cmd &)

Every command line terminal is a shell process , The programs you execute in this terminal are actually this shell Sub processes divided by processes . Under normal circumstances ,shell The process will block , Wait for the subprocess to exit before receiving the new command you entered . add & Number , Just let shell The process is no longer blocked , You can continue to respond to your new orders . But anyway , If you turn this off shell Command line port , All subprocesses attached to it will exit .

and (cmd &) Run the command like this , It is take cmd The order hangs on a systemd Under the name of system daemons , recognize systemd Be a father , So when you exit the current terminal , For what just happened cmd The order has no effect at all .

nohup

nohup some_cmd &

nohup The principle is very simple , After the terminal is shut down, it will send SIGHUP The signal , While using nohup The running process will Ignore this signal , Therefore, the process will not exit after the terminal is shut down .

Compare

(cmd &) This form is more stable