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3009 :: Progress Bar using stdout.write and eraseLine()

• alfrednewman (orginal) [2017-06-20T14:31:05+02:00] view original

  Hello,

  I'm trying to create a simple progress bar indicator. I'd like to print (update) the bar always in the same line of the screen. Looking at the source code of choosenim, I discovered eraseLine(). So, I made the following toy code:

  import strutils, terminal
  
  proc showBar(content: string) =
      eraseLine()
      stdout.write("[$1]" % [content])
      stdout.flushFile()
  
  var lastPos = 0
  var content = repeat(' ', 10)
  for progress in 0..<10:
      content[lastPos] = '#'
      lastPos.inc()
      showBar(content)
  Run

  However, I am getting an error.

  Traceback (most recent call last)
  temp.nim(13)             temp
  terminal.nim(660)        showBar
  terminal.nim(389)        eraseLine
  os.nim(154)              raiseOSError
  Error: unhandled exception: Invalid Identifier.
   [OSError]
  Run

  Without the eraseLine(), the result is the following:

  [#         ][##        ][###       ][####      ][#####     ][######    ][#######   ][########  ][######### ][##########]
  Run

  What am I doing wrong ?

  TIA

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• mashingan (orginal) [2017-06-20T15:45:11+02:00] view original

  You are using undefined eraseLine proc

  The correct is stdout.eraseLine()

  import strutils, terminal
  from os import sleep
  
  proc showBar(content: string) =
    stdout.eraseLine
    stdout.write("[$1]" % [content])
    stdout.flushFile
  
  var content = ' '.repeat 10
  for progress in 0 ..< 10:
    content[progress] = '#'
    sleep 100
    showBar content
  Run

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• Krux02 (orginal) [2017-06-20T17:27:19+02:00] view original

  Instead of eraseLine you can also always print "\r". That character does not erase the line, but puts the write cursor back at the beginning of the line. output after that overrides what is already there. So in this case, where you always print the full length of the progress bar, the effect is the same as eraseLine.

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• alfrednewman (orginal) [2017-06-20T21:59:53+02:00] view original

  All the best guys !

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• euant (orginal) [2017-06-22T11:05:57+02:00] view original

  I also have a handy library in Nimble to simplify creating progress bars that might help too: https://github.com/euantorano/progress.nim

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• alfrednewman (orginal) [2017-06-22T12:42:47+02:00] view original

  Nice job Euan ! Thanks.

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