Compatibility with non-tty devices

lib/progressbar.rb

@@ -37,7 +37,6 @@ def initialize (title, total, out = STDERR)
 
   private
   def fmt_bar
-    bar_width = do_percentage * @terminal_width / 100
     sprintf("|%s%s|", 
             @bar_mark * bar_width, 
             " " *  (@terminal_width - bar_width))
@@ -63,6 +62,10 @@ def fmt_title
     @title[0,(@title_width - 1)] + ":"
   end
 
+  def bar_width
+    do_percentage * @terminal_width / 100
+  end
+
   def convert_bytes (bytes)
     if bytes < 1024
       sprintf("%6dB", bytes)
@@ -138,6 +141,12 @@ def get_width
   end
 
   def show
+    tty? ? show_tty : show_no_tty
+    @previous_time = time_now
+  end
+
+  # Print output to a tty device.
+  def show_tty
     arguments = @format_arguments.map {|method| 
       method = sprintf("fmt_%s", method)
       send(method)
@@ -155,7 +164,25 @@ def show
       @terminal_width += width - line.length + 1
       show
     end
-    @previous_time = time_now
+  end
+
+  # Print output to a non-terminal device, such as a log file.
+  # The terminal width is set to 80 columns.
+  def show_no_tty
+    @out.print("| " + elapsed + eol) and return if finished?
+
+    # Draw title the first time
+    if @last_bar_width.nil?
+      @last_bar_width = 0
+      @terminal_width = @terminal_width - fmt_title.size - elapsed.size - 4
+      @out.print(fmt_title + " |")
+    else
+      bar_width_change = bar_width - @last_bar_width
+      if bar_width_change > 0
+        @out.print(@bar_mark * bar_width_change)
+        @last_bar_width = bar_width
+      end
+    end
   end
 
   def show_if_needed
@@ -186,8 +213,13 @@ def time_now
     end
   end
 
+  def tty?
+    @out.tty?
+  end
+
   public
   def clear
+    return unless tty?
     @out.print "\r"
     @out.print(" " * (get_width - 1))
     @out.print "\r"

test.rb

@@ -1,5 +1,5 @@
 require 'test/unit'
-require 'lib/progressbar'
+require File.expand_path('../lib/progressbar', __FILE__)
 
 class ProgressBarTest < Test::Unit::TestCase
   SleepUnit = 0.01
@@ -138,6 +138,20 @@ def test_delorean
     }
     pbar.halt
   end
+
+  class StubbedTtyProgressBar < ProgressBar
+    def tty?; false; end
+  end
+
+  def test_non_tty
+    total = 1024 * 1024
+    pbar = StubbedTtyProgressBar.new("non-tty compatible", total)
+    0.step(total, 2**14) {|x|
+      pbar.set(x)
+      sleep(SleepUnit)
+    }
+    pbar.finish
+  end
 end
 
 class ReversedProgressBarTest < ProgressBarTest