Run a Detached Program (daemon) from a Linux Shell Command Line Prompt.

Simon Tite 6:55 am on November 5, 2009 | Answers: 1    
Tags: daemon (3), detached, from (4), linux (74), linux shell (5), program (10), run (36), shell (14), shell command line, unix (43)

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• Simon Tite 6:55 am on November 5, 2009
  

  nohup any-command &

  This is something I find useful, when I might need to edit a file I have just found, but I don’t want to tie up the terminal session, and as I’m already in a terminal session, I don’t want to have to mouse around the screen to start my editor, navigate to the file, open it, etc. Neither do I want the editor to terminate if I accidentally terminate the terminal session.

  Example:
  nohup edit myfile.txt &

  Explanation for the morbidly curious:

  The ampersand at the end of any shell command means “run in a separate process”. This spawns a new shell to run the command, however the new shell is dependent on the calling shell: when the calling shell terminates, so will the child shell.

  The nohup command tells the root process to spawn as a child of the root process, thus it will continue to live on, even when its parent dies…

  “nohup” as far as I know owes its name to the days of dial-in timeshare systems, where you would be charged by the minute actually connected to the system. Using “nohup”, you could spawn a lengthy process, then hang up (disconnect) the telephone, and return later to see the results of the job, avoiding excessive connect time. “nohup” means “no hang up”.