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From: Helmut Waitzmann <nn.throttle@xoxy.net>
Newsgroups: comp.unix.shell
Subject: Re: nohup Versus setsid
Date: Fri, 13 Sep 2024 19:00:45 +0200
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 Lawrence D'Oliveiro <ldo@nz.invalid>:
> It has long seemed to me that nohup(1) was an old, hacky way of=20
> doing what can be done more elegantly using setsid(1). Compare=20
> the docs for yourself=20
> <https://manpages.debian.org/1/nohup.1.en.html> vs=20
> <https://manpages.debian.org/1/setsid.1.en.html>, and tell me=20
> why we still need nohup when we have setsid?=20
>

 Because there is a real difference between both of them.=20


 "nohup" makes the invoked command immune to the HUP signal but=20
 lets it remain in its terminal session, i.=E2=80=AFe.=C2=A0the command to =
be=20
 run will not lose its controlling terminal.=C2=A0 Thus the other job=20
 control signals like TSTP, INT, and QUIT sent by the terminal=20
 driver to the command may have their effects.=20


 Also, the HUP signal will be ignored regardless of its origin=20
 (terminal driver as well as the "kill(2)" system call).=20


 If, on the other hand, you use "setsid", the command to be run=20
 will not be made immune to any of the job control signals,=20
 i.=E2=80=AFe.=C2=A0any job control signal sent to the command to be run by=
=20
 means of the kill(2) system call will have its effect.=20


 Also, as the command to be run will leave the terminal session=20
 and thus lose the controlling terminal of the invoker, it won't=20
 be affected by any job control signal sent by the terminal driver=20
 of the invoker's controlling terminal, for example when typing=20
 the interrupt, suspend or quit key on the keyboard no signal will=20
 reach the command to be invoked.=20