gnome-shell 使用 notify-send 发送桌面消息

       notify-send - a program to send desktop notifications

       notify-send [OPTIONS] <summary> [body]

       With notify-send you can sends desktop notifications to the user via a notification daemon
       from the command line.  These notifications can be used to inform the user about an  event
       or display some form of information without getting in the user's way.

       -u, --urgency=LEVEL Specifies the urgency level (low, normal, critical).

       -t, --expire-time=TIME
              The duration, in milliseconds, for the notification to appear on screen.  (Ubuntu's
              Notify OSD and GNOME Shell both ignore this parameter.)

       -i, --icon=ICON[,ICON...]
              Specifies an icon filename or stock icon to display.

       -c, --category=TYPE[,TYPE...]
              Specifies the notification category.

          Help options:

       -?, --help
              Show this help message

       -h, --hint=TYPE:NAME:VALUE
              Specifies basic extra data to pass. Valid types are int, double, string and byte.

       SEE ALSO
              The Desktop Notification Spec on http://www.galago-project.org/specs/notification/.

       This manual page was written by Andre Filipe de Assuncao e  Brito  <decko@noisemakers.org>
       and  Paul  van Tilburg <paulvt@debian.org> and Riccardo Setti <giskard@debian.org> for the
       Debian project (but may be used by others).
在 gnome-shell 中 使用 notify-send --help 命令来进行显示使用说明：

➜  Downloads notify-send --help
Usage:
  notify-send [OPTION?] <SUMMARY> [BODY] - create a notification

Help Options:
  -?, --help                        Show help options

Application Options:
  -u, --urgency=LEVEL               Specifies the urgency level (low, normal, critical).
  -t, --expire-time=TIME            Specifies the timeout in milliseconds at which to expire the notification.
  -a, --app-name=APP_NAME           Specifies the app name for the icon
  -i, --icon=ICON[,ICON...]         Specifies an icon filename or stock icon to display.
  -c, --category=TYPE[,TYPE...]     Specifies the notification category.
  -h, --hint=TYPE:NAME:VALUE        Specifies basic extra data to pass. Valid types are int, double, string and byte.
  -v, --version                     Version of the package.