fish lacks manual disown capability/command, in case we want running, owned jobs to stop upon terminal exit

[Pysis868]

I wanted to effectively 'disown' jobs/processes like I do in bash, manually.

I have found out that this happens automatically (#773) (Fish User Discussions - "disown" command in fish), but feel there may be some that would like it to be a manual process. As the following steps highlight, some may want jobs to be started with the intent of stopping when the parent terminal session exits.

Also, I have not found this explanation of the functionality in the official documentation (fish shell - Commands - jobs). Could this be added?

Reproduction Steps:

~> jobs
jobs: There are no jobs
~> sleep 12m &
~> jobs
Job Group   State   Command
1   68591   running sleep 12m &
~> ps aux|grep sleep
user          68602   0.0  0.0  2424084    336 s001  R+    4:13PM   0:00.00 grep --color=auto sleep
user          68591   0.0  0.0  2434840    752 s001  S     4:13PM   0:00.00 sleep 12m
~> exit

Open a new terminal

~> ps aux|grep sleep
user          68876   0.0  0.0  2423980    220 s001  R+    4:14PM   0:00.00 grep --color=auto sleep
user          68591   0.0  0.0  2434840    752   ??  S     4:13PM   0:00.00 sleep 12m

Expected behavior:

sleep 12m would not still be running.

Observed behavior:

sleep 12m is still running.

Additional information:

• Slightly (Un)related: "disown" in fish shell #1247

---

Fish version: fish, version 2.2.0

Operating system: Mac OS X El Capitan 10.11.3.
I seem to have forgotten how I have installed fish, my terminal histories don't have it. I would say it's (Home)brew, and it does state fish is Poured from bottle.

Terminal or terminal emulator: iTerm2 ("xterm-256color")

[krader1961]

I'm opposed to implementing a bash like "disown" command since, among other things, it would require changing the current behavior in a non-backward compatible manner. I do agree the current behavior should be documented including rationale for why fish does this by default rather than requiring the user use nohup or disown.

[krader1961]

Note that as of fish 2.5.0 we no longer automatically disown backgrounded jobs. Fish now behaves like bash, zsh, etc. and sends SIGHUP to them when the shell exits. This increases the need to implement a disown command.

[fgrsnau]

I would argue that this is no longer a feature request but a bug/regression as all custom fish function relying on this behaviour now fail.

[krader1961]

You can argue that point all you want, @fgrsnau, but you're wrong. The behavior you prefer was introduced by commit bff68f3 in March 2015 to address the misguided request in issue #1771. Note that what was originally asked for was support for bash syntax like (kate &). That "works" in bash because the backgrounded job is not launched by the shell in which you type that command -- it's launched by a subshell. So the kate command is not in the job table of your interactive shell and thus won't be sent a SIGHUP. The person who opened that issue was not asking that all background jobs of the current interactive shell be immune to SIGHUP. Then 1player chimed in with a comment that is clearly wrong. Unfortunately that convinced @zanchey implement the behavior I recently reverted because people were surprised by it. See issue #3497. It is unfortunate that no one at the time recognized that the proper fix for the request in issue #1771 was to add a disown command rather than make that the default behavior.

The nohup command is the traditional solution to keep a background job from being killed. A disown command, ala bash, simply makes it possible to retroactively achieve the same result if you forget to use nohup. We would be happy to expeditiously review and merge a patch from yourself or anyone else willing to do the work to implement a disown command.

[krader1961]

Until someone implements disown you can either use nohup or the double-fork trick: fish -c 'emacs &'. Either one can be implemented as a function. For example:

function disown
    nohup $argv </dev/null >/dev/null 2>&1 &
end

or

function disown
    set -l escaped_argv (string escape --no-quoted $argv)
    fish -c "$escaped_argv &"
end

You can get completions for the actual command by using the same trick as the sudo completion. Assuming you name the function disown:

complete -c disown -d "Command to run" -x -a "(__fish_complete_subcommand)"

[jonhoo]

Unfortunately that implementation of disown does not allow you to retroactively disown a a process.

[krader1961]

That is true, @jonhoo. The workaround I posted does not let you retroactively disown an already running job. It does, however, make it easy to do so if you know up front that is what you want which is the usual case. I'm hoping someone like yourself who feels passionate about this will take the time to create a patch that we can review and merge which implements a full-featured implementation.

[jonhoo]

@krader1961 it wasn't meant as criticism, just as an observation :)