Put a process started with ! in the background

Question

If I do this from the shell:

$ sleep 100

I can make it go to the background by doing:

^Z
$ bg

And then continue using my shell. You can get the same effect by adding a & to the end of the command, but I often forget this.

In Vim, I often do:

:!sleep 100

And here also, I often forget to add the &. Can I put this process in the background and continue using Vim like in the shell?

Answer 1

As <C-z> will suspend Vim itself, not just the launched shell command, that won't work.

What I would do is abort the long-running command with <C-c>, then relaunch the same command in the background via

:!! &

(The :!! command comes handy for recalling the previous external command here; you could also use the Ex command history via <Up>.)

Answer 2

You can put the command in a shell script that backgrounds itself. The contents, for example, might be:

#!/bin/sh
sleep 100 &

Answer 3

Normally when a process is started, you don't have much control on it other than terminating it (Ctrl+c) or suspending it (Ctrl+z, but including the parent process).

However depending on the process type and operating system, here are few tricks that you can try:

• Sending SIGTSTP or SIGSTOP will stop the process (the same signal sent by Ctrl+z), and SIGCONT will continue (resume) the process. Testing with sleep doesn't work, so you've to test it with specific software how it handles the signals. E.g.

  killall -SIGSTOP sleep
  killall -SIGTSTP sleep
  kill -SIGTSTP PID
  

  SIGSTOP stop process stop (cannot be caught or ignored)

  SIGTSTP stop process stop signal generated from keyboard

• Sending SIGHUP to the process. By default this signal terminates the process, however if the process implements SIGHUP signal, it should detach from controlling tty and re-run in the background with new process id (usually it's used with daemons). Unfortunately many applications do not handle it correctly and simply die (including sleep). E.g.

  killall -SIGHUP sleep
  

  SIGHUP terminate process terminal line hangup

• Other solution could use tools such as retty (reattach to a pseudo-tty), detach (detaches a process from the terminal), nohup (disconnects the process from the terminal) or gdb (attach to existing process -p and close its file descriptors such as tty, similar example).

For more info, check: Job control (Unix) - Implementation at Wikipedia.

See also: man kill or man sigaction.

Answer 4

Note: This answer only seems to work with the tcsh and fish shells. I also tried bash, dash, mksh, and zsh, and it doesn't work there; I'm not sure why, because if I do the same actions from these shells without Vim, it does work as expected... (:! commands are executed though the shell).

I happen to use tcsh, so it works for me...

You can use :set shell=/bin/tcsh to set your shell; this is global, though. So only use it if you think this is a very important feature :-)

---

^Z send a SIGTSTP signal, you can send this signal with kill, and then use SIGCONT to continue (resume) the process. This will detach the process from Vim.

Because it's difficult to show with this sleep (how do you know it has continued execution?), I'll use gitk as an example (but any GUI program will do):

For example in Vim:

:!gitk %

And then in another terminal:

$ ps ax | grep gitk
30105 pts/10   S+     0:00 -bin/tcsh -c gitk
30108 pts/10   Sl+    0:00 wish /sbin/gitk --

$ kill -TSTP 30108
$ kill -CONT 30108

You can of course also use killall, or pkill; for example:

$ killall -TSTP wish
$ killall -CONST wish

You do need to open another terminal for this, which is not ideal, but it will allow you to continue using both your Vim and your external process.