如何从systemd用户服务访问会话D总线？

Question

我有运行shell脚本的用户服务，它试图访问会话的锁定屏幕状态，如下所示：

# Test Unity screen-lock:
isLocked() {
    isLocked=$(gdbus call -e -d com.canonical.Unity -o /com/canonical/Unity/Session -m com.canonical.Unity.Session.IsLocked)
}

lock() {
  if [[ $isLocked == "(false,)" ]]; then                                                                                                     
        gnome-screensaver-command -l
  elif [[ $isLocked == "(true,)" ]]; then                                                                                                
        exit 1
  fi
exit 0
}

问题是服务“是每个用户的进程，而不是每个会话”，我不知道如何访问会话dbus：

GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name com.canonical.Unity was not provided by any .service files

Answer 1

我也面临着同样的问题，而我的研究却一无所获。如果有人能找到更好的方式来查询联合的锁状态，我很想听听它。

我最近了解了命名管道，当时我想知道我可能会用这样的东西做什么。事实证明，这个问题恰好是一个完美的应用程序。

创建以下脚本..。

#!/bin/bash
# this script is meant to be called in two different ways.
# 1.    It can be called as a service by passing "service" as the first argument. In this 
#   mode, the script listens for requests for lock screen status. The script should be
#   run in this mode with startup applications on user logon.
# 2.    If this script is called without any arguments, it will call the service to request
#   the current lock screen status. Call this script in this manner from your user 
#   service.

# this will be the named pipe we'll use for requesting and receiving screen lock status
pipe="/tmp/lockscreen-status"

if [ "$1" == "service" ]; then
    # setup the named pipe
    rm "$pipe"
    mkfifo "$pipe"

    # start watching for requests
    while true
    do
        # watch the pipe for trigger events requesting lock screen status
        read request < "$pipe"

        # respond across the same pipe wit the current lock screen status
        gdbus call -e -d com.canonical.Unity -o /com/canonical/Unity/Session -m com.canonical.Unity.Session.IsLocked | grep -oP "(true)|(false)" > "$pipe"
    done
else
    # make sure the pipe exists
    if [ ! -e "$pipe" ]; then
        echo "This script must started in service mode before lock status can be queried."
        exit
    fi

    # send a request for screen lock status and read the response
    touch "$pipe"
    read status < "$pipe"

    [ "$status" == "" ] && status="This script must started in service mode before lock status can be queried."

    # print reponse to screen for use by calling application
    echo $status
fi

正如注释中所指出的，您需要以两种方式调用此脚本。当用户登录时，以服务模式启动此脚本。我使用“启动应用程序”程序来调用脚本，但是它的调用方式并不重要，只要它在登录时被用户帐户调用就行了。然后，在您的用户服务中，只需调用此脚本，如果屏幕被锁定，它将返回"true“，如果屏幕被解锁，则返回"false”。