Feature #13604

Exposing alternative interface of readline

Added by graywolf (Gray Wolf) over 1 year ago. Updated about 1 year ago.

Target version:


GNU Readline has multiple modes of operation. At the moment, the readline extension only supports typical, Readline.readline mode. However, there is also alternative callback-based interface which is also useful.

require_relative 'readline'

PROMPT = "rltest$ "

$running = true
$sigwinch_received = false

Readline.handler_install(PROMPT, add_hist: true) do |line|
    # Can use ^D (stty eof) or `exit' to exit.
    if !line || line == "exit"
        puts unless line
        puts "exit"
        $running = false
        puts "input line: #{line}"

Signal.trap('SIGWINCH') { $sigwinch_received = true }

while $running do
    rs =[$stdin])
    if $sigwinch_received
        $sigwinch_received = false
    Readline.read_char if r = rs[0]

puts "rltest: Event loop has exited"

Patch adding support for this is attached. This is my first try at contributing to ruby, so please tell me what I did wrong (I'm sure something, C is not my strong language).


readline_alternative_interface.diff (7.22 KB) readline_alternative_interface.diff Patch graywolf (Gray Wolf), 05/27/2017 10:00 AM
readline_alternative_interface_example.rb (606 Bytes) readline_alternative_interface_example.rb How it can be used? graywolf (Gray Wolf), 05/27/2017 10:00 AM
readline_alternative_interface_update1.diff (7.08 KB) readline_alternative_interface_update1.diff improved version graywolf (Gray Wolf), 05/29/2017 06:34 PM


Updated by shevegen (Robert A. Heiler) over 1 year ago

All improvements to Readline are great - I can't have commandline user interfaces in ruby (on linux) without Readline these days. :)

The only thing that I think isn't too great is the use of global variables. Is it possible to get rid of them?

Updated by graywolf (Gray Wolf) over 1 year ago

It should be possible. The bool is easy (I just set it on Readline module just like I do the handler block and I try to find a way to pass char * inside VALUE. I'll find a way and post updated patch.

I don't really see a benefit though, it's not like you can use Readline multiple times at once anyway, underlying C library doesn't support it (afaict).

Updated by graywolf (Gray Wolf) over 1 year ago

I think I managed to simplify it quite a bit, if you would take a look :)

Also I'm thinking about exposing the add_hist setting, since it's saved on mReadline anyway, it would allow user to dynamicly enable/disable auto-adding of history between each invocation of read_char. What do you think?

Updated by hsbt (Hiroshi SHIBATA) over 1 year ago

  • Assignee set to kouji (Kouji Takao)
  • Status changed from Open to Assigned

kouji (Kouji Takao) or nobu (Nobuyoshi Nakada)

Can you review this patch?

Updated by graywolf (Gray Wolf) about 1 year ago

any update on this?

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