In-place progress output in the terminal or console

Question

Use carriage return. '\r' should usually work.

git/progress.c

...
        eol = done ? done : "   \r";
...
                fprintf(stderr, "...%s", ..., eol);
                fflush(stderr);

Git simply emits a carriage return and no line feed, which the terminal interprets as "move to first column".

You'll have to use another method (like Curses) to update two lines in-place.

ablogaboutcode.com | web.archive.org

...and...

http://www.ruby-doc.org/stdlib-1.9.3/libdoc/curses/rdoc/Curses.html

I wrote little class for multiline output update:

class ConsoleReset
  # Unix
  # Contains a string to clear the line in the shell
  CLR = "\e[0K"
  # ANSI escape sequence for hiding terminal cursor
  ESC_CURS_INVIS = "\e[?25l"
  # ANSI escape sequence for showing terminal cursor
  ESC_CURS_VIS   = "\e[?25h"
  # ANSI escape sequence for clearing line in terminal
  ESC_R_AND_CLR  = "\r#{CLR}"
  # ANSI escape sequence for going up a line in terminal
  ESC_UP_A_LINE = "\e[1A"

  def initialize
    @first_call = true
  end

  def reset_line(text = '')
    # Initialise ANSI escape string
    escape = ""

    # The number of lines the previous message spanned
    lines = text.strip.lines.count - 1

    # Clear and go up a line
    lines.times { escape += "#{ESC_R_AND_CLR}#{ESC_UP_A_LINE}" }

    # Clear the line that is to be printed on
    # escape += "#{ESC_R_AND_CLR}"

    # Console is clear, we can print!
    STDOUT.print escape if !@first_call
    @first_call = false
    print text
  end

  def hide_cursor
    STDOUT.print(ESC_CURS_INVIS)
  end

  def show_cursor
    STDOUT.print(ESC_CURS_VIS)
  end

  def test
    hide_cursor

    5.times do |i|
      line = ['===========================================']
      (1..10).each do |num|
        line << ["#{num}:\t#{rand_num}"]
      end
      line << ['===========================================']
      line = line.join("\n")
      reset_line(line)
      sleep 1
    end

    show_cursor

    puts ''
  end

  private
    def rand_num
      rand(10 ** rand(10))
    end
end

Inspired by prydonius/spinning_cursor. See test method for example usage.