# Long Running Sessions

## Setup box

### Long Running Sessions

Using solutions like `screen` or `mosh` can help workaround `ssh` hang-ups which can kill any child processes of an active ssh session.

#### Screen

* How do I start `screen`, during an active `ssh` session?
  * `screen`
    * will start a screen session with a random name
    * `screen -S SESSIONNAME` is good for starting a session with a name
* How do I list any pre-existing `screen` sessions?
  * `screen -ls`
* How to I re-attach or re-join a previous session?
  * `screen -r previous_session_name`
* How do I force detach and then reattach a previous session?
  * `screen -d -r previous_session_name`
* How do I rename a pre-existing `screen` session?
  * `screen -S old_session_name -X sessionname new_session_name`
* How to [check](https://serverfault.com/questions/257975/how-to-check-if-im-in-screen-session) if I'm in a `screen` session?
  * `echo $STY`
    * If you are inside a screen session, the output will be the session name
    * otherwise, the output will be empty
* How do I find my current `screen` session's name?
  * `echo $STY`
* How do I kill a `screen` session?
  * `screen -X -S <SESSION_ID> quit`
* How do I kill my current `screen` session?

  ```
    screen -X -S `echo -n $STY` quit
  ```
* How do I [scroll](http://serverfault.com/questions/206303/how-to-scroll-back-in-screen-within-a-ssh-session-from-os-x)?
  * Inside the `screen` session you can use: `CTRL+A (release), [`
    * You can then use the arrows to scroll around the window. To get out of scrolling you can use `CTRL+C`
  * `Ctrl + A, ESC` and then vim-like commands: `Ctrl + u or Ctrl + d`
  * You can [modify](http://slaptijack.com/system-administration/mac-os-x-terminal-and-gnu-screen-scrollback/) `.screenrc` to allow mouse-based scrollback.

    ```
      # added on july 19 2017 by pulkit
      # after editing the source from: https://gist.github.com/ChrisWills/1337178

      # GNU Screen - main configuration file
      # All other .screenrc files will source this file to inherit settings.
      # Author: Christian Wills - cwills.sys@gmail.com

      # Allow bold colors - necessary for some reason
      attrcolor b ".I"

      # Tell screen how to set colors. AB = background, AF=foreground
      termcapinfo xterm 'Co#256:AB=\E[48;5;%dm:AF=\E[38;5;%dm'

      # Enables use of shift-PgUp and shift-PgDn
      termcapinfo xterm|xterms|xs|rxvt ti@:te@

      # Erase background with current bg color
      defbce "on"

      # Enable 256 color term
      term xterm-256color

      # Cache 999999 lines for scroll back
      defscrollback 999999

      hardstatus alwayslastline

      # Very nice tabbed colored hardstatus line
      hardstatus string '%{= Kd} %{= Kd}%-w%{= Kr}[%{= KW}%n %t%{= Kr}]%{= Kd}%+w %-= %{KG} %H%{KW}|%{KY}%101`%{KW}|%D %M %d %Y%{= Kc} %C%A%{-}'

      # Hide hardstatus: ctrl-a f
      bind f eval "hardstatus ignore"

      # Show hardstatus: ctrl-a F
      bind F eval "hardstatus alwayslastline"
    ```