Well, if you work always in tmux/screen (a recommended practice for operations, that I did import to my daily shell activity) you don't need job control.
When there is a "surprisingly slow" command, then just press the shortcut for a new screen session.
Will get alerted in the status bar when the slow command finishes.
Output of each command will be in it's own screen session (not mixed).
That Ctrl + z response was no for issue1, but for the wishes of the second sentence of @hibbelig.
I meant to include the part of capturing the output -- the part that Ctrl+Z does not do.
Opening a new screen/tmux session is a cool idea, but the new session doesn't inherit the state from the already running one, I guess. (At least in screen, not sure about tmux.) By "state" I mean the shell history, the current working directory, the (environment) variables.
Also, say that long running command runs five minutes, and after one minute you create a new session. Then after four more minutes you now have two sessions, both ready to accept input. Which one do you use to continue working? How do you know which one to close?
My screen respects the current working directory for new sessions.
My history is configured to write at every prompt redraw and to don't miss commands.
With vanilla history and prompt command settings, history will be separated.
But as this is a common problem, and not only with screen, also with multiple xterms and IDE's shells, and... also is a problem that history may miss lines by default...
And as it's a common problem, there are settings to fix that, configure the history merge strategy to your taste and do not miss history lines, because you did close a xterm, or you did open a new screen sessions.
Curiously, those settings are even documented upstream.
Session variables? I expect the ones that could be loaded by login executing bash -l...
If I did export something after that, then maybe I simply need to export it again in a new session, but really in 20 years never was in this situation I think... (do not wait to a command, continue with other commands, and need a environment variable not initialized by default between both sessions....). If I was in that situation... was so easy to fix that I don't even remember.
Which one to close? the one I prefer randomly, probably by focus, or probably the highest screen id. As history is merged, I can close any or even both.
What you are asking for, "post-redirection" (a term I just coined) is not an easy task. Redirection is, but that's set up prior to the program run (warning: pseudocode ahead):
child = fork()
if child == 0 then
stdout = open("output","w")
stderr = open("error","w")
dup2(stdout,FILENO_STDOUT)
dup2(stderr,FILENO_STDERR)
Close(stdout)
Close(stderr)
Execve("someprogram",arglist,envlist)
End
Standard Unix stuff. But doing that after the program is running isn't easy. The only way I know of is to send the program SIGSTOP (stops execution of the program---said signal can't be caught), and using ptrace(), inject code into the process to open the output file and call dup2() to get the redirection going, calling said code, then resuming the program.
I suppose one could script gdb (or whatever Unix debugger exists on the suystem) to do such a thing, but the fact that no one has really done this might mean something.