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mike
Asked: 2009-07-02 14:16:44 +0800 CST

Is it possible to detach a process from its terminal? (Or, "I should have used screen!") [duplicate]

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Possible Duplicate:
Can I nohup/screen an already-started process?

On Unix (specifically, Linux), I've started a job in a regular ssh->bash session. I'd like to leave work soon, but I now realize that the job is going to take several hours.

If I had just started this job in screen, I could detach and go home. But I didn't.

Is there any way to disconnect the job from its ssh session, so I can shut down my computer, (dropping the TCP connection and killing the ssh session), and yet have the program keep running?

I don't care about its output -- in fact, I redirected stdout to a file. I just want it to run to completion.

linux unix gnu-screen

9 Answers

  1. You can press ctrl-z to interrupt the process and then run bg to make it run in the background.

    You can show a numbered list all processes backgrounded in this manner with jobs.

    Then you can run disown %1 (replace 1 with the process number output by jobs) to detach the process from the terminal.

    In spite of the name, the process will still be owned by you after running disown, it will just be detached from the terminal you started it in.

    This answer has more information

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  2. I believe the command you are looking for is "disown"

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  3. Use

    nohup command &

    Is beautiful:

    root@index:~# nohup /usr/bin/curl localhost/begemot.php &
[1] 894
root@index:~# nohup: ignoring input and appending output to `nohup.out'

    and exit of this terminal, a task proceed to be continued...

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  4. From within your bash shell:

    control+z

    Then, to continue running the job in background:

    bg

    Later, you can type jobs to see if your process is still running.

    • 10

  5. When using reptyr inside screen, you can move the process (or its output) into screen.

    • 8

  6. I have taken to setting up screen to auto-run when I connect to hosts I use regularly, to avoid this issue.

    http://tlug.dnho.net/?q=node/239 is one way of doing it, though there are other variations out there.

    Has saved me once or twice when I've had an unexpected disconnection mid-session and would otherwise have forgotten to start screen before I started something long-winded.

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  7. Using crtl-Z then bg or using & when running the command is not reliable at 100%. It will work in most case but may not work as expected in some case (I/O usage, ...).
    Screen is a reliable solution.

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  8. If you are using bash, you can suspect with control-Z and background with bg.

    Job control (from man bash)

     If the operating system on which bash is running supports job 
 control, bash contains facilities to use it.   Typing the  
 suspend  character  (typically ^Z, Control-Z) while a process 
 is running causes that process to be stopped and returns control 
 to bash.  Typing the delayed suspend character (typically ^Y, 
 Control-Y) causes the process  to  be stopped  when  it  
 attempts to read input from the terminal, and control to be 
 returned to bash.

    help bg

    bg: bg [job_spec ...]
    Place each JOB_SPEC in the background, as if it had been started with
    `&'.  If JOB_SPEC is not present, the shell's notion of the current
    job is used.

    help jobs

    jobs: jobs [-lnprs] [jobspec ...] or jobs -x command [args]
    Lists the active jobs.  The -l option lists process id's in addition
    to the normal information; the -p option lists process id's only.
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  9. If you know beforehand that you want to have it running in the background, the unix command at is a good option. It starts commands in the background at scheduled time, just like a cron job that does not repeat. Depending on your distribution, you might need to install it and to start the atd daemon.

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