Ruby Console Input Character by Character

Question

I'd like to get an input string of digits (multiples of 5) in one line, but after each block of 5 digits, a space separator character would print to make the input line easier to read and count.

For instance:

Enter random numeric key with a length of 25 digits below:

45325 89345 98834 23453 23453

Rather than:

Enter random numeric key with a length of 25 digits below:

4532589345988342345323453

Is this at all possible?

---

I tried using getc to read in a character but am getting an error message:

undefined local variable or method `getc' for main:Object (NameError)

Answer 1

You could do something like this:

require 'io/console'

cnt=0
buffer=[]
while cnt<25 do
    c=STDIN.getch 
    if c=~/[0-9]/ then 
        print c
        print " " if (cnt+=1)%5==0
        buffer<<c
    else
        IO::console::beep
    end
end    

puts "\n#{buffer.join}"

As written, it does what you stated. But typically something would also need to support delete, esc and ^ c at a minimum.

Here is a way to handle those (but I bet there is a better way):

#!/usr/bin/env ruby

require 'io/console'

def get_line(txt, len=25, skip=5)
    def left
        IO::console::cursor_left(1)
    end 
    
    def pr(c)
        print c
    end 
    
    def del(x)
        x.times{left()} 
        x.times{pr(' ')}
        x.times{left()} 
    end         
    
    def beep
        IO::console::beep
    end 
        
    cnt=col=0
    buf=[]
    breaks=["\u0003"]
    bs=["\x0008", "\u007F"]
    print txt
    line=""
    
    while buf.length<len do
        c=STDIN.getch 
        if c=~/[0-9]/ then 
            buf << c
        elsif bs.include?(c) 
            buf.length>0 ? buf.pop : beep()
        elsif breaks.include?(c) 
            buf=[]
            break
        elsif c=="\e" 
            buf=[]
        else     
            beep()
        end
        del(line.length)
        line=buf.map.with_index(1){|c,i| 
            "#{c}#{(i%skip==0) ? " " : ""}"
        }.join
        line.chars.each{|c| pr(c) }
    end    
    buf.join
end 

p get_line("Enter numbers: ")

Or an alternate version that uses a case statement rather than the if elsif else ladder:

require 'io/console'

def get_line(txt, len=25, skip=5)
    def left 
        IO::console::cursor_left(1) 
    end 
    def pr(c) 
        print c 
    end 
    def del(x)
        x.times{left()} 
        x.times{pr(' ')}
        x.times{left()} 
    end         
    
    beep=-> {IO::console::beep}
    backspace=lambda{|c| ["\x0008", "\u007F"].include?(c) }
    brk=lambda{|c| ["\u0003"].include?(c) }
        
    cnt=col=0; buf=[]; line=""

    print txt
    
    while buf.length<len do
        c=STDIN.getch 
        case c
        when /[0-9]/ 
            buf << c
            
        when backspace
            buf.length>0 ? buf.pop : beep[]
            
        when brk 
            buf=[]
            break
            
        when "\e" 
            buf=[]
            
        else     
            beep[]
        end
        del(line.length)
        line=buf.map.with_index(1){|c,i| 
            "#{c}#{(i%skip==0) ? " " : ""}"
        }.join
        line.chars.each{|c| pr(c) }
    end    
    buf.join
end 
# works the same

The problem is that there is a great deal of variability in text terminal types, compliance and capabilities. These functions only needs left, pr and beep to work properly on the terminal you use so not that hard. You could do it with ANSI codes as well.