What does the ampersand (&) symbol mean with `nohup`

nohup

Ive seen tons of examples where a & follows the end of a command string, but I can't seem to find an explanation on what it does. It's not even in nohup's man page. Is this a shell thing?

Either using & or not, I find that any process ran with nohup seems to exhibit immunity to any hangup signal.

Best Answer

From the bash manpage:

If a command is terminated by the control operator &, the shell executes the command in the background in a subshell. The shell does not wait for the command to finish, and the return status is 0.

So yes, it's a shell thing, and can be used with any command. It essentially returns control to you immediately and allows the command to complete in the background. This is almost always used with nohup because you typically want to exit the shell after starting the command.

Related Solutions

Windows – There is any way to run processes in the background in Windows? nohup equivalent for windows

You can use the start command to run a process in the background of the command window.

command1
command2
start command3
command4

command2 waits until command1 finish but command4 don't wait that command3 finishes.

and if you need to run independently of the user logged on, you need to start the process as a service and you can use anysrv.exe

Reattaching a process started with nohup

You can use tools such as reptyr to reattach a running process to a new terminal, generally speaking though it's a lot simpler to plan ahead and simply launch the process inside screen or tmux - that way you don't need nohup, and you can connect/disconnect at will.

Best Answer

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Windows – There is any way to run processes in the background in Windows? nohup equivalent for windows

Reattaching a process started with nohup

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