Bash：获取守护屏幕会话的 PID
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Bash: Getting PID of daemonized screen session
提问by hexacyanide
If I start a GNU screen session as a daemon, how would I retrieve its PID programmatically? I don't know how consistent the output of screen -lsis, so I'd like to know how to do this with one of bash's constants, $$, $!or a better alternative.
如果我将 GNU 屏幕会话作为守护程序启动，我将如何以编程方式检索其 PID？我不知道如何输出一致 screen -ls的，所以我想知道如何使用bash的常量之一，做到这一点$$，$!还是更好的选择。
I am starting the screen with screen -dmS screenname.
我用screen -dmS screenname.
How would I get the PID of a screen right before or immediately after starting the screen session?
如何在开始屏幕会话之前或之后立即获取屏幕的 PID？
回答by sarnold
This show the pid for a screen named nameofscreen:
这显示了名为 的屏幕的 pid nameofscreen：
$ screen -ls
There are screens on:
19898.otherscreen (07/03/2012 05:50:45 PM) (Detached)
19841.nameofscreen (07/03/2012 05:50:23 PM) (Detached)
2 Sockets in /var/run/screen/S-sarnold.
$ screen -ls | awk '/\.nameofscreen\t/ {print strtonum()}'
19841
$
回答by fess .
you can use:
您可以使用：
screen -DmS nameofscreen
which does not fork a daemon process allowing you to know the pid.
它不会分叉守护进程，让您知道 pid。
Parsing the output of screen -ls can be unreliable if two screen sessions have been started with the same name. Another approach is to not let the screen session fork a process and put it in the background yourself:
如果两个 screen 会话以相同的名称启动，则解析 screen -ls 的输出可能不可靠。另一种方法是不要让屏幕会话派生一个进程并自己将其置于后台：
For example with an existing initial screen session:
例如，对于现有的初始屏幕会话：
fess@hostname-1065% screen -ls
There is a screen on:
19180.nameofscreen (01/15/2013 10:11:02 AM) (Detached)
create a screen using -D -m instead of -d -m which does not fork a new process. Put it in the background and get it's pid. (Using posix shell semantics)
使用 -D -m 而不是 -d -m 创建一个屏幕，它不会分叉新进程。把它放在后台并得到它的pid。（使用 posix shell 语义）
fess@hostname-1066% screen -DmS nameofscreen &
[3] 19431
fess@hostname-1067% pid=$!
Now there are two screens both have the same name:
现在有两个屏幕都具有相同的名称：
fess@hostname-1068% screen -ls
There are screens on:
19431.nameofscreen (01/15/2013 10:53:31 AM) (Detached)
19180.nameofscreen (01/15/2013 10:11:02 AM) (Detached)
but we know the difference:
但我们知道区别：
fess@hostname-1069% echo $pid
19431
and we can accurately ask it to quit:
我们可以准确地要求它退出：
fess@hostname-1070% screen -S $pid.nameofscreen -X quit
[3] - done screen -DmS nameofscreen
now there's just the original one again:
现在又只有原来的了：
fess@hostname-1071% screen -ls
There is a screen on:
19180.nameofscreen (01/15/2013 10:11:02 AM) (Detached)
回答by dotancohen
You can get the PID of the screen sessions here like so:
您可以在此处获取屏幕会话的 PID，如下所示：
$ screen -ls
There are screens on:
1934.foo_Server (01/25/15 15:26:01) (Detached)
1876.foo_Webserver (01/25/15 15:25:37) (Detached)
1814.foo_Monitor (01/25/15 15:25:13) (Detached)
3 Sockets in /var/run/screen/S-ubuntu.
Let us suppose that you want the PID of the program running in Bash in the foo_Monitorscreen session. Use the PID of the foo_Monitorscreen session to get the PID of the bashsession running in it by searching PPIDs (Parent PID) for the known PID:
让我们假设您想要在foo_Monitor屏幕会话中在 Bash 中运行的程序的 PID 。使用foo_Monitorscreen 会话的 PIDbash通过搜索已知 PID 的 PPID（父 PID）来获取在其中运行的会话的 PID：
$ ps -el | grep 1814 | grep bash
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
0 S 1000 1815 1814 0 80 0 - 5520 wait pts/1 00:00:00 bash
Now get just the PID of the bashsession:
现在只获取bash会话的 PID ：
$ ps -el | grep 1814 | grep bash | awk '{print }'
1815
Now we want the process with thatPID. Just nest the commands, and this time use the -vflag on grep bashto get the process that is notbash:
现在我们想要具有该PID的进程。只需嵌套命令，这次使用-v标志 ongrep bash来获取不是bash的进程：
echo $(ps -el | grep $(ps -el | grep 1814 | grep bash | awk '{print }') | grep -v bash | awk '{print }')
23869
Just replace 1814 with the real PID or your screen session:
只需将 1814 替换为真实的 PID 或您的屏幕会话：
echo $(ps -el | grep $(ps -el | grep SCREEN_SESSION_PID | grep bash | awk '{print }') | grep -v bash | awk '{print }')
回答by Alan Curry
I suspect you really want the PID of the program running inside screen, which doesn't seem to be easily available. (And not really a well-defined question, since a single screen process can manage multiple children - that's one of the great things about screen!)
我怀疑您真的想要在屏幕内运行的程序的 PID，这似乎不容易获得。（并不是一个真正定义明确的问题，因为单个屏幕进程可以管理多个子项 - 这是屏幕的一大优点！）
You could use pgrep to find a process whose PPID is the screen PID. Or do something like this:
您可以使用 pgrep 来查找其 PPID 是屏幕 PID 的进程。或者做这样的事情：
rm mypidfile
screen -dmS blah sh -c 'echo $$ > mypidfile ; exec sh'
# the write to mypidfile is happening in the background, so wait it to show up
while [ ! -s mypidfile ]; do sleep 1; done
pid=`cat mypidfile`
# $pid is now the PID of the shell that was exec'ed inside screen
回答by Nagisa
This answer is inspired by @sarnold.
这个答案的灵感来自@sarnold。
Let me add a way to get all the screen PID:
让我添加一种获取所有屏幕 PID 的方法：
screen -ls | awk '/[0-9]{1,}\./ {print strtonum()}'
Since 0-299 is the PID of the daemon in the old kernel, you can change {1,} to {3,}
由于 0-299 是旧内核中守护进程的 PID，因此您可以将 {1,} 更改为 {3,}
You can operate on each process in the following ways, such as exiting them.
您可以通过以下方式对每个进程进行操作，例如退出它们。
pidList=(screen -ls | awk '/[0-9]{3,}\./ {print strtonum()}')
for pid in ${pidList[@]};
do
screen -X -S $pid quit
done
You can also do some other things with screen -X -S $pid stuff 'command\n'.
您还可以使用screen -X -S $pid stuff 'command\n'.
回答by Lars Schillingmann
Another way is using screen's -Q parameter for querying the session:
另一种方法是使用 screen 的 -Q 参数来查询会话：
screen -S nameofscreen -Q echo '$PID'
Note that this will also display the PID inside the screen session as a notification.
请注意，这还将在屏幕会话中显示 PID 作为通知。
回答by user3093815
To complete sarnold's answer:
要完成 sarnold 的回答：
$ screen -ls
There are screens on:
19898.otherscreen (07/03/2012 05:50:45 PM) (Detached)
19841.nameofscreen (07/03/2012 05:50:23 PM) (Detached)
2 Sockets in /var/run/screen/S-sarnold.
$ screen -ls | awk '/\.nameofscreen\t/ {print strtonum()}'
19841
... get the PIDs of processes with this PID as PPID as follows:
...获取具有此 PID 作为 PPID 的进程的 PID，如下所示：
$ ps --ppid 19841 -o pid=
19842
