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如何在单个命令行中为“update-alternatives --config gdm3.css”分配优先级编号？

tag-icon • tag-icon command-line gnome themes gdm update-alternatives
如何在单个命令行中为“update-alternatives --config gdm3.css”分配优先级编号？

我可以在终端中运行以下命令：

$ sudo update-alternatives --install /usr/share/gnome-shell/theme/gdm3.css gdm3.css /usr/share/gnome-shell/theme/mytheme/mytheme.css 10
$ sudo update-alternatives --config gdm3.css
There are 2 choices for the alternative gdm3.css (providing /usr/share/gnome-shell/theme/gdm3.css).

  Selection    Path                                                    Priority   Status
------------------------------------------------------------
* 0            /usr/share/gnome-shell/theme/ubuntu.css                  10        auto mode
  1            /usr/share/gnome-shell/theme/mytheme/mytheme.css         10        manual mode
  2            /usr/share/gnome-shell/theme/ubuntu.css                  10        manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/share/gnome-shell/theme/mytheme/mytheme.css to provide /usr/share/gnome-shell/theme/gdm3.css (gdm3.css) in manual mode

我会将这两个cmd放在python3.6 subprocess.run()中。

我遇到的问题与第二条命令有关。如何在与相同的命令行中将指定/usr/share/gnome-shell/theme/mytheme/mytheme.css为 的替代方案？gdm3.csssudo update-alternatives --config gdm3.css

此外，此命令需要输入数字才能选择mytheme.css。分配的数字取决于分配的优先级，这意味着分配的数字可能非常随意。如何克服分配的数字的随意性？

答案1

根据@PRATAP的评论，我开发了这个python3.6解决方案来解决我的问题。它在我的Ubuntu 18.04系统上运行良好。我希望它能帮助有同样需求的人。

#!/usr/bin/env python3.6
# -*- coding: utf-8 -*-

from subprocess import run, PIPE
from pathlib import Path
import mimetypes

class CSSFileTypeError(Exception):
    pass

class GDM3_alternatives:
    '''Class to query and configure gdm3.css.

    Argument:
      mytheme - path to my gnome-shell theme .css file.

    Attributes:
      mytheme - path to my gnome-shell theme .css file.
      query   - stdout from "update-alternatives --query gdm3.css" store in a list
      link    - gdm3.css path
      best    - gdm3.css alternative path selected by auto mode 
      value   - current gdm3.css alternative path 
      status  - whether gdm3.css is selected by manual or automatic mode 
      max     - maximum Priority value of all the installed gdm3.css alternatives

    Methods:
      exist()     - determines whether "mytheme" is installed as a gdm3.css alternative.
      configure() - configure "mytheme" file as a gdm3.css alternative.
    '''
    def __init__( self, mytheme=None ):       
        def _get( qvalue ):
            return [ line[ line.index('/') : ] for line in self.query if qvalue in line ][0]
        self.mytheme = mytheme
        self.query = run( [ 'update-alternatives', '--query', 'gdm3.css' ],
                          stdout=PIPE, encoding="utf-8" ).stdout.splitlines()
        self.link   = _get( 'Link:' )
        self.best   = _get( 'Best:' )
        self.value  = _get( 'Value:' )
        self.status = [ line[ line.index(':')+2 : ] for line in self.query if 'Status:' in line ][0]
        self.max = max( [ int( line[ line.index(':')+1 : ] ) for line in self.query if 'Priority:' in line ] )
        #print( f'self.query = {self.query}' )  #For debugging
        #print( f'self.link  = {self.link}' )   #For debugging
        #print( f'self.best  = {self.best}' )   #For debugging
        #print( f'self.value = {self.value}' )  #For debugging
        #print( f'self.status= {self.status}' ) #For debugging
        #print( f'self.max   = {self.max}' )    #For debugging

    def exist( self ):
        '''Method that determines whether "mytheme.css" is installed as a gdm3.css alternative. '''
        if self.mytheme == None:
            raise TypeError( '.css file was not defined.' ) 
        if not Path( self.mytheme ).exists():
            raise FileNotFoundError( f'{self.mytheme} does not exist.' )
        if 'css' not in mimetypes.guess_type( self.mytheme )[0] :
            raise CSSFileTypeError( f'{self.mytheme} is not a css file.' )
        return True in [ True for line in self.query if self.mytheme in line ]

    def configure( self ):
        '''Method to configure my theme ".css" file as a gdm3.css alternative.'''
        def _config():
            if 'auto' not in self.status:
                run( [ 'update-alternatives', '--auto', 'gdm3.css' ] ) #Ensure auto mode is used
            run( [ 'update-alternatives', '--install', self.link, 'gdm3.css', self.mytheme, str(self.max + 1) ] )
            print( f'Configured {self.mytheme} as gdm3.css alternative.' )

        if not self.exist():
            _config()
        elif self.value in self.mytheme:
            print( f'{self.mytheme} is already gdm3.css alternative.' )
        else:
            run( [ 'update-alternatives', '--remove', 'gdm3.css', self.mytheme ] )
            self.__init__( self.mytheme )
            _config()

if __name__ == '__main__':
    #mytheme = '/usr/share/gnome-shell/theme/mytheme/mytheme.css' 
    mytheme = '/usr/share/gnome-shell/theme/mytheme/mytheme.css' #Change this to your theme
    gdm3 = GDM3_alternatives( mytheme )
    gdm3.configure()

## This script needs to be executed by sudo. ##

如何使用这个脚本：

  1. 将其保存为带扩展名的文件.py，例如myscript.py。
  2. 更改行mytheme = '/usr/share/gnome-shell/theme/mytheme/mytheme.css'以显示您的主题的.css路径。
  3. 在终端上运行脚本使用 sudo 权限，即输入sudo python3.6 myscript.py。或者使用权限打开你的python IDLEsudo并运行这个python脚本。

我的Ubuntu 18.04系统上的版本update-alternatives是：

$ update-alternatives --version
Debian update-alternatives version 1.19.0.5.

This is free software; see the GNU General Public License version 2 or
later for copying conditions. There is NO warranty.

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