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DenisZ
Asked: 2021-06-01 03:37:20 +0800 CST

Howto start and detach screen with user environment on startup?

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I want to start screen and put a couple of programs running inside on startup. I've seen many similar posts but none answered my question. so I put in rc.local following 2 lines:

  screen -dmS scr bash -c 'ytop; exec bash'
  screen -S scr -X screen 1 bash -c 'nvtop; exec bash'

which works fine, but when I enter this screen, once logged in to the server, and want to create new screen, it doesn't have environment variables in it. How can I start it in the way that would have all root's envars?
new window looks like this:

sh-5.1#

$PATH in window is
/usr/bin:/bin

Yet in the rc.local created windows $PATH (/usr/bin:/bin) is the same, but the prompt is normal, so it looks that it reads /etc/profile
Window initialized by rc.local has normal prompt:

[root@mysrv ~]#

PATH is also a bit more than fresh window, but not same as if I start screen manually from the terminal as root

echo $PATH
usr/lib64/qt-3.3/bin:/usr/bin:/bin


When I start screen by myself it's normal prompt.

[root@mysrv ~]#

and

echo $PATH
/usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin

Interestingly if I exit ytop it shows me proper prompt. Only when creating new screen somehow looses this envars.
I tried also running:

su - root -c `screen -dmS scr bash -c 'ytop; exec bash'`

but I get the same result.
Regards

bash gnu-screen shell-scripting

2 Answers

  1. I think your problem here is the session-handling of bash. Bash - like any other shell interpreter - detects if it is started in the backgroud, or if it is attached to a terminal ( Interactive / Non-interactive mode ). Background is found here. My guess is, that your problems are solved by providing the -l switch to the first bash command:

    screen -dmS scr bash --login -c 'ytop; exec bash'

    The --login switch makes bash read all startup files, like /etc/profile, ~/.bash_profile, ~/.bash_login, and ~/.profile - which should contain the environmental variables you are missing.

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  2. I finally found a solution. It's very simple. So to start screen with normal shell and variables you have to do it with init, so :

    su - root -c `screen -dmS scr bash -c 'ytop; exec init'`

    So this will have normal environment like if you manually start screen and detach it.

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