Question

I want to build an application with a text based UI that is similar to the Linux command ‘top’, in Ruby. What toolkits and/or techniques can I use to build the UI? In particular I want an area of the console window that is constantly updating, and the ability to press keys to manipulate the display.

Answer 1

Ncurses is great for console apps and you can find bindings for it for lots of languages (or just use shell scripting). There’s even a cursed gtk (http://zemljanka.sourceforge.net/cursed/) though I think work on it stopped quite awhile back.

You didn’t mention your platform, but for OS/X there’s a great little app called Geektool (http://projects.tynsoe.org/en/geektool/) which allows you to put script output on your desktop. I use a small ruby script to generate my top processes list:

puts %x{uptime}

IO.popen("ps aruxl") { |readme|
    pslist = readme.to_a
    pslist.shift # remove header line
    pslist.each_with_index { |i,index|
      ps = i.split
      psh = { user: ps[0], pid: ps[1], pcpu: ps[2], pmem: ps[3],
              vsz: ps[4], rss: ps[5], tty: ps[6], stat: ps[7],
              time: ps[8], uid: ps[9], ppid: ps[10], cpu: ps[11], pri: ps[12], 
              nice: ps[13], wchan: ps[14], cmd: ps[16..ps.size].join(" ") }
      printf("%-6s %-6s %-6s %s", "PID:", "%CPU:", "%Mem", "Command\n") if index == 0
      printf("%-6d %-6.1f %-6.1f %s\n", 
        psh[:pid].to_i, psh[:pcpu].to_f, psh[:pmem].to_f, psh[:cmd]) if index < 10

    }

}

(This could probably be better, but it was the first ruby script I ever wrote and since it works I’ve never revisited it to improve it – and it doesn’t take input. Anyway, it might help give you some ideas)