From: Luo Yong <cyberblue.yong@...>
Date: 2006-11-13T01:02:35+09:00
Subject: Re: Controlling readline

On 11/12/06, Paul Lutus <nospam@nosite.zzz> wrote:
> Luo Yong wrote:
>
> > On 11/12/06, Paul Lutus <nospam@nosite.zzz> wrote:
> >> Luo Yong wrote:
> >>
> >> > Hi all
> >> >
> >> > Is there anyway to control the maxium length of the IO.readline can
> >> > read?
> >>
> >> Not really, not from the command line. You can throw away all the length
> >> you don't want once it has been entered. It is way better to expect more
> >> characters than you get than to get more than you expect (long sad story
> >> about C/C++ "gets" snipped here).
> >>
> >> Maybe you should describe the problem, rather than asking about this way
> >> of solving it.
> >>
> >> --
> >> Paul Lutus
> >> http://www.arachnoid.com
> >>
> >>
> >
> > I'm writing an RPC program.I use readline to read the command.I'm
> > afraid that my program can be attacked by others if I can't limit the
> > maxium length the readline can read.So I'm finding a way to control
> > it.
>
> As written, "readline" won't read more than it can safely store, which is
> what you are after. Your concern arose from such things as "gets",
> mentioned in my last post, that wrote beyond its allocated buffer because
> it didn't know its length.
>
> Why don't you read a character at a time, then stop reading characters after
> you have what you want? Like this:
>
> -----------------------------------
>
> #!/usr/bin/ruby -w
>
> max = 16
>
> while true
>
>   print "Type something:"
>   STDOUT.flush
>
>   input = STDIN.sysread(max)
>
>   puts "\nYou entered (in chunks of #{max} chars) #{input}."
>
> end
>
> -----------------------------------
>
> This routine reads the input in chunks of "max" characters, and continues to
> cycle through similarly sized chunks indefinitely. Linefeeds are not
> special to it, although that would be easy to add. This gives you a limit
> on input size, but you then have to sort out for yourself what a line is,
> and where one ends and another begins.
>
> --
> Paul Lutus
> http://www.arachnoid.com
>
>

This may be the best way.

Thanks a lot.