☰

如何檢查螢幕會話是否正在運行？

tag-icon • tag-icon bash gnu-screen
如何檢查螢幕會話是否正在運行？

有沒有辦法檢查螢幕會話是否正在 bash 中運行？
例如：

if [screen is running]
  then
    screen -r          #if session is running then resume the session
  else
    screen "command"   #else start a new session
fi

答案1

利用PPID(Parent PID) 環境變量，並從

$ ps -fp$PPID
UID        PID  PPID  C STIME TTY          TIME CMD
w3       19305 19304  0 00:00 ?        00:00:00 SCREEN
+w3@aardvark:~(0)$

或者，

ps -fp$PPID | head -n 2 | tail -n 1 | egrep -q SCREEN
screen_is_running=$((1 - ${PIPESTATUS[-1]}))
# screen_is_running == 1 for yes, 0 for No, -1 for egrep error

$PPID當然，如果您已經產生、執行、nohup 或其他操作，並且使您的螢幕不被屏蔽，那麼這將不起作用。

如果是這種情況，您可以使用pgrep,建立一些pstree可以egrep沿著$PPID鏈返回的東西（當為 1 時停止$PPID）。

答案2

透過閱讀，man screen您會發現COMMAND LINE OPTIONS：

COMMAND-LINE OPTIONS
       Screen has the following command-line options:

    ...snip...

       -d -r   Reattach a session and if necessary detach it first.

       -d -R   Reattach a session and if necessary detach or even create it first.

       -d -RR  Reattach a session and if necessary detach or create it. Use the first session if more than one session is available.

       -D -r   Reattach a session. If necessary detach and logout remotely first.

       -D -R   Attach  here  and now. In detail this means: If a session is running, then reattach. If necessary detach and logout remotely first.  If it was not running create it and notify
               the user. This is the author's favorite.

       -D -RR  Attach here and now. Whatever that means, just do it.

            Note: It is always a good idea to check the status of your sessions by means of "screen -list".

當然，其中之一可以在沒有變數的情況下完成您想要的操作。

相關內容