How to override or edit the last printed lines in a ruby CLI script? - ruby

Question

I am trying to build a script that gives me feedback about progress on the command-line. Actually it is just putting a newline for every n-th progress step made. Console looks like
10:30:00 Parsed 0 of 1'000'000 data entries (0 %)
10:30:10 Parsed 1'000 of 1'000'000 data entries (1 %)
10:30:20 Parsed 2'000 of 1'000'000 data entries (2 %)
[...] etc [...]
11:00:00 Parsed 1'000'000 of 1'000'000 data entries (100 %)
Even if timestamp and progressnumbers are fictional, you should see the problem.
What I want is to do it "wget-style" with a progressbar updated on the command line, with linewidth in mind.
First I thought about the use of curses because I had hands on as I tried to learn C, but I never could get warm with it, also I think it is bloated for the purpose of manipulating just a few lines. Also I dont need any coloring. Also most other libraries I found seemed to be specialized for coloring.
Can someone help me with this problem?

Answer 1

A while ago I created a class to be a status text on which you can change part of the content of the text within the line. It might be useful to you.
The class with an example use are:
class StatusText
def initialize(parms={})
#previous_size = 0
#stream = parms[:stream]==nil ? $stdout : parms[:stream]
#parms = parms
#parms[:verbose] = true if parms[:verbose] == nil
#header = []
#onChange = nil
pushHeader(#parms[:base]) if #parms[:base]
end
def setText(complement)
text = "#{#header.join(" ")}#{#parms[:before]}#{complement}#{#parms[:after]}"
printText(text)
end
def cleanAll
printText("")
end
def cleanContent
printText "#{#parms[:base]}"
end
def nextLine(text=nil)
if #parms[:verbose]
#previous_size = 0
#stream.print "\n"
end
if text!=nil
line(text)
end
end
def line(text)
printText(text)
nextLine
end
#Callback in the case the status text changes
#might be useful to log the status changes
#The callback function receives the new text
def onChange(&block)
#on_change = block
end
def pushHeader(head)
#header.push(head)
end
def popHeader
#header.pop
end
def setParm(parm, value)
#parms[parm] = value
if parm == :base
#header.last = value
end
end
private
def printText(text)
#If not verbose leave without printing
if #parms[:verbose]
if #previous_size > 0
#go back
#stream.print "\033[#{#previous_size}D"
#clean
#stream.print(" " * #previous_size)
#go back again
#stream.print "\033[#{#previous_size}D"
end
#print
#stream.print text
#stream.flush
#store size
#previous_size = text.gsub(/\e\[\d+m/,"").size
end
#Call callback if existent
#on_change.call(text) if #on_change
end
end
a = StatusText.new(:before => "Evolution (", :after => ")")
(1..100).each {|i| a.setText(i.to_s); sleep(1)}
a.nextLine
Just copy, paste in a ruby file and try it out. I use escape sequences to reposition the cursor.
The class has lots of features I needed at the time (like piling up elements in the status bar) that you can use to complement your solution, or you can just clean it up to its core.
I hope it helps.

Answer 2

In the meanwhile I found some gems that give me a progressbar, I will list them up here:
ProgressBar from paul at github
a more recent version from pgericson at github
ruby-progressbar from jfelchner at github
simple_progressbar from bitboxer at github
I tried the one from pgericson and that from jfelchner, they both have pros and cons but also both fits my needs. Probably I will fork and extend one of them in the future.
I hope this one helps others to find faster, what I searched for months.

Answer 3

Perhaps replace your outputting to this:
print "Progress #{progress_var}%\r"