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控制台中的简单进度指示

发布于 2024-12-28 06:10:19 字数 101 浏览 2 评论 0原文

在控制台中指示工作进度的最简单方法是什么？输出百分比就够了，不需要进度条。

仅使用 print 会产生很多行，我只想在终端中使用一个变化的字符串。

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与往事干杯 2025-01-04 06:10:19

最简单的方法是像 wget 和其他程序一样：在进度信息之前打印出回车符和 ANSI 擦除行代码，从而将光标返回到行的开头并替换现有文本。例如：

import Control.Monad
import Control.Concurrent
import System.IO
import Text.Printf

putProgress :: String -> IO ()
putProgress s = hPutStr stderr $ "\r\ESC[K" ++ s

drawProgressBar :: Int -> Rational -> String
drawProgressBar width progress =
  "[" ++ replicate bars '=' ++ replicate spaces ' ' ++ "]"
  where bars = round (progress * fromIntegral width)
        spaces = width - bars

drawPercentage :: Rational -> String
drawPercentage progress = printf "%3d%%" (truncate (progress * 100) :: Int)

main :: IO ()
main = do
  forM_ [0..10] $ \i -> do
    let progress = fromIntegral i / 10
    putProgress $ drawProgressBar 40 progress ++ " " ++ drawPercentage progress
    threadDelay 250000
  putProgress "All done."
  hPutChar stderr '\n'

这里的关键是不打印换行符，以便您可以在下一次进度更新时返回到行的开头。

当然，您可以在此处打印出百分比并删除栏，但栏更酷:)

The simplest way would be to do what wget and other programs do: printing out a carriage return and an ANSI erase-line code before the progress information, thus returning the cursor to the start of the line and replacing the existing text. For example:

import Control.Monad
import Control.Concurrent
import System.IO
import Text.Printf

putProgress :: String -> IO ()
putProgress s = hPutStr stderr $ "\r\ESC[K" ++ s

drawProgressBar :: Int -> Rational -> String
drawProgressBar width progress =
  "[" ++ replicate bars '=' ++ replicate spaces ' ' ++ "]"
  where bars = round (progress * fromIntegral width)
        spaces = width - bars

drawPercentage :: Rational -> String
drawPercentage progress = printf "%3d%%" (truncate (progress * 100) :: Int)

main :: IO ()
main = do
  forM_ [0..10] $ \i -> do
    let progress = fromIntegral i / 10
    putProgress $ drawProgressBar 40 progress ++ " " ++ drawPercentage progress
    threadDelay 250000
  putProgress "All done."
  hPutChar stderr '\n'

The key thing here is to not print a newline, so that you can return to the start of the line on the next progress update.

Of course, you could just print out the percentage here and drop the bar, but a bar is cooler :)

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