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如何检查屏幕会话是否正在运行？

tag-icon • tag-icon bash gnu-screen
如何检查屏幕会话是否正在运行？

有没有办法检查屏幕会话是否在 bash 中运行？
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）环境变量，并从

$ 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

当然，如果您已经生成、执行、nohup 或执行了其他操作，并且没有使屏幕显示，那么这将不起作用$PPID。

如果是这种情况，您可以用 、 构建一些东西，pgrep可以沿着链条往回走（当为 1 时停止）。pstreeegrep$PPID$PPID

答案2

通过阅读man screen你会发现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".

当然，其中一个可以在没有变量的情况下完成你想要做的事情。

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