From: Robert Klemme <shortcutter@...>
Date: 2012-07-04T15:44:18+09:00
Subject: Re: ARGF: No switch to STDIN after all files?

On Wed, Jul 4, 2012 at 4:03 AM, Iazel Datenshi <lists@ruby-forum.com> wrote:
> I've started learning Ruby and trying to do the first (stupid) program
> as exercise.
> The input will be supported from a file and/or stdin.
> If no file given, the program prompt user to insert all the data.
> If a file is given, it expects line with at least two integers and will
> read until the first bad line. After that, we expect another valid line.
> If while reading the first sequence the file(s) end, a feature require
> the user to insert some other data.
> And there's the problem!

> Also if ARGV is empty, ARGF doesn't swap to STDIN and gets continue to
> return nil.

ARGF switches to $stdin only if ARGV is empty *initially*, i.e. when
the first read attempt is made.

> I've tried ARGV.rewind, but got an ArgumentError "no stream to rewind".
>
> So, is there a method to swap to STDIN after reading all files? Thanks
> in advance :)

You can push "-" onto ARGV which will make ARGF switch to STDIN - this
even works when you have read from ARGF already:

~$ seq 20 25 | ruby19 -e '2.times { ARGF.each {|l| printf "%s:
%s",ARGF.filename,l}; ARGV << "-" }' <(seq 10 15)
/dev/fd/63: 10
/dev/fd/63: 11
/dev/fd/63: 12
/dev/fd/63: 13
/dev/fd/63: 14
/dev/fd/63: 15
-: 20
-: 21
-: 22
-: 23
-: 24
-: 25

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/