From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-06-18T01:17:38+09:00
Subject: Re: stubborn program using readline

On Fri, 17 Jun 2005, Wybo Dekker wrote:

> On Thu, 16 Jun 2005, Logan Capaldo wrote:
>
>> Theory: readline reads from STDIN correct? using rltest < rltest means
>> that STDIN gets EOF, which means STDIN is closed which means readlien
>> can't read anything from it.
>
> No, readline should not necessarily read from STDIN. It can read from the
> console, /dev/tty or so.
>
>> I don't think you can have your cake and
>> eat it too in this case. If you want the interactive prompt your going
>> to have pass the file name on the command line instead of using IO
>> redirection. I'm a bit confused as to the purpose of this.
>
> What I want is a program that reads data from either a file or STDIN and
> then lets the user run various commands on those data.

put another way - you want the program to ALWAYS read from EITHER a file or
stdin and you ALWAYS want to interactively (eg. from a tty) run commands after
reading the file - so why not just say that in the code?

   #
   # program which does the above
   #
     jib:~ > cat a.rb
     require 'readline'
     include Readline

     inpath = ARGV.shift
     infile = inpath ? open(inpath) : STDIN

     # count lines in stdin (the mail message):
     n=0; while infile.gets: n+=1 end
     puts "#{n} lines"

     # always get commands interactively
     STDIN.reopen '/dev/tty' unless STDIN.tty?
     readline("type return to quit: ")
     puts "quitting..."

   #
   # reading interactively from stdin and typing ctrl-D
   #
     jib:~ > ruby a.rb
     one
     two
     three
     3 lines
     type return to quit:
     quitting...

   #
   # reading non-interactively from stdin
   #
     jib:~ > ruby a.rb < a.rb
     13 lines
     type return to quit:
     quitting...

   #
   # reading from file
   #
     jib:~ > ruby a.rb a.rb
     13 lines
     type return to quit:
     quitting...


you could take other approaches with dup'ing and forking but this might work
for you.

hth.

-a
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