求助：Conky中两个Lua函数无法独立更新的问题

我编写了两个Lua函数getSongLyrics和getSongTitle，用于在Conky窗口展示内容：

• getSongLyrics通过Python脚本执行sptlrx pipe，将结果输出到FIFO文件后读取，再通过conky_displaySongLyrics展示
• getSongTitle借助playerctl获取当前播放歌曲的歌手与标题，通过conky_displaySongTitle直接展示

当前存在的问题：

• 切换歌曲时，getSongTitle的输出仅在getSongLyrics更新（出现新歌词行）时才会刷新
• 若播放无歌词的歌曲，conky_displaySongLyrics始终不更新，conky_displaySongTitle也会停留在上一首歌曲的信息，直到播放有歌词的歌曲才会更新

推测是FIFO文件等待sptlrx pipe新内容导致的阻塞问题，希望实现两个函数独立运行、互不影响。

scripts.lua #

-- read file and print contents of file
function readPrintFile(file)
    local f = io.open(file, "rb")
    
    -- if file doesn't exist, return nil
    if not f then return nil end

    local content = f:read("*a")
    f:close()

    return content
end

-- get song title from a music source
function getSongTitle()
    local command = io.popen("playerctl metadata --player spotify --format '{{ artist }} - {{ title }}'", "r")
    local title = command:read("*l")
    command:close()
    return format:gsub("\n", "")
end

-- get song lyrics from a music source
function getSongLyrics()
    local lyrics = readPrintFile("/tmp/sptlrx_lyrics") or ""
    return lyrics:gsub("\n", "")
end

function conky_displaySongTitle()
    return getSongTitle()
end

function conky_displaySongLyrics()
    return getSongLyrics()
end

sptlrx_lyrics.py #

import os
import subprocess

pipe_path_lyrics = "/tmp/sptlrx_lyrics"
try:
    os.mkfifo(pipe_path_lyrics)
except FileExistsError:
    pass

process_lyrics = subprocess.Popen(["sptlrx", "pipe"], stdout=subprocess.PIPE)

for line_lyrics in iter(process_lyrics.stdout.readline, ""):
    with open(pipe_path_lyrics, "wb") as lyrics:
        lyrics.write(line_lyrics)

conky.conf #

conky.config = {
    lua_load = "$HOME/.config/conky/scripts.lua",
    ...
}

conky.text = [[
${if_running spotify}\${alignc} ${lua displaySongTitle}
${alignc} ${lua displaySongLyrics}\...
${endif}
]]

问题根源 #

Conky默认同步执行所有Lua函数，而FIFO文件是阻塞式读取——如果sptlrx pipe没有新内容写入，io.open或read操作会卡住整个Conky的更新循环，导致getSongTitle无法执行。

具体修改步骤 #

1. 修复Lua函数的bug并实现非阻塞读取FIFO
   首先修正getSongTitle里的变量错误，再修改readPrintFile为非阻塞读取：

   -- 非阻塞读取文件内容
   function readPrintFile(file)
       local f = io.open(file, "rb")
       if not f then return "" end
       -- 设置非阻塞模式
       f:setvbuf("no")
       -- 用pcall捕获读取阻塞的异常
       local ok, content = pcall(function() return f:read("*a") end)
       f:close()
       -- 读取失败则返回空字符串
       return ok and content or ""
   end
   
   -- 获取歌曲标题（修复变量错误）
   function getSongTitle()
       local command = io.popen("playerctl metadata --player spotify --format '{{ artist }} - {{ title }}'", "r")
       local title = command:read("*l") or ""
       command:close()
       return title:gsub("\n", "")
   end
   

2. 优化Python脚本，监听歌曲切换事件
   原脚本仅在有歌词时写入FIFO，切换无歌词歌曲时不会更新。修改后添加歌曲切换监听，主动清空FIFO：

   import os
   import subprocess
   import select
   
   pipe_path_lyrics = "/tmp/sptlrx_lyrics"
   try:
       os.mkfifo(pipe_path_lyrics)
   except FileExistsError:
       pass
   
   # 启动sptlrx获取歌词，同时用playerctl监听歌曲切换
   sptlrx_proc = subprocess.Popen(["sptlrx", "pipe"], stdout=subprocess.PIPE, text=True)
   playerctl_proc = subprocess.Popen(
       ["playerctl", "metadata", "--player", "spotify", "--follow", "--format", "changed"],
       stdout=subprocess.PIPE, text=True
   )
   
   def write_fifo(content):
       try:
           with open(pipe_path_lyrics, "w") as f:
               f.write(content.strip() + "\n")
       except Exception:
           pass
   
   # 初始写入空内容
   write_fifo("")
   
   while True:
       # 非阻塞监听两个进程的输出
       read_streams, _, _ = select.select([sptlrx_proc.stdout, playerctl_proc.stdout], [], [], 1)
       
       for stream in read_streams:
           line = stream.readline().strip()
           if stream == sptlrx_proc.stdout and line:
               write_fifo(line)
           elif stream == playerctl_proc.stdout:
               # 歌曲切换时清空歌词
               write_fifo("")
       
       # 进程退出则终止循环
       if sptlrx_proc.poll() is not None or playerctl_proc.poll() is not None:
           break
   

3. 调整Conky更新配置
   在conky.config中确保足够的更新频率：

   conky.config = {
       lua_load = "$HOME/.config/conky/scripts.lua",
       update_interval = 1, -- 每秒更新一次
       lua_draw_hook_pre = "", -- 确保Lua函数每次更新都执行
       ...
   }
   

内容的提问来源于stack exchange，提问作者Anapal