Mettere un programma in background con "screen"

Today we talk about screen: a small utility command line for Linux systems.

Screen, quite simply, he's able to multiply the terminals at our disposal, of undock a terminal by its process and maintain active process in the background (by returning the terminal to use).

Screen is particularly useful when it launches a command that requires a response time rather long (such as a backup) be it launched locally or on a remote server. The timeout of the server or the user accidentally kill could lead to an interruption command and frustrate the time spent.

But let's see how it works:

`screen`	start screen and returns the shell
`screen + comando`	start the program “command” inside “screen”
Once started “`screen`“
“`ctrl+a`” and then “`c`“	creates a new terminal
“`ctrl+a`” and then “`n`“	skips to the next terminal
“`ctrl+a`” and then “`p`“	switches to the previous terminal
“`ctrl+a`” and then “`d`“	“unhooks” screen from the session

Once unhooked from the session can end the SSH tunneling or close the terminal. The program will continue to run in the background.

To retrieve a previous session will take “hang up”:

`screen -list`	lists all the started sessions
`screen -r`	retrieves a previously started session

Below is one example of the terminal with two sessions “dropped” The screen.

joe@joe-desktop:~$ screen -d
There are screens on:
16268.pts-3.joe-desktop (01/12/2019 20:58:09) (Detached)
23799.pts-4.joe-desktop (01/12/2019 16:30:08) (Detached)
There is no screen to be detached.
joe@joe-desktop:~$

To “hang up” to a specific session just specify the PID. I our case “screen -r 16268“.

To clear a screen that is the command: screen -X -S {PID della sessione} kill.