From: Wybo Dekker <wybo@...>
Date: 2005-06-17T07:41:22+09:00
Subject: Re: stubborn program using readline

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. 

To be more specific, it's a program (vpp, http://www.servalys.nl/scripts/vpp)
that I have written in Perl and it reads a PDF (or PostScript) file, 
displays it, and after this offers the user a command prompt where she can 
choose to print some pages, or all pages, in various formats (booklet, 
one-sided, two-sided), either to a printer or to an other PDF file.

PDF (or PostScript) files can be offered to it:

vpp some_pdf_or_postscript_file

or piped to it:

vpp <some_pdf_or_postscript_file

The latter is particularly useful if, for example, you want to print 
selected pages from a man page. For example:

man -t ruby |vpp

This worked fine in Perl, but can't be done in the Ruby version which 
I'm trying to make...

I quess you cannot translate the following Perl script into Ruby

   #!/usr/bin/perl -w
   
   # showline - read lines from stdin,
   #            then let user interrogate lines by number
   
   my @x;
   while (<>) {
      push(@x,$_);
   }
   
   use Term::ReadLine;
   my $t=new Term::ReadLine 'vpp';
   
   while ( (my $n = $t->readline("type line number (0 to stop): ")) > 0) {
      if ( $n > @x) {
         print "no such line\n";
      } else {
         print "line $n: $x[$n-1]";
      }
   }
   
and then run it like so:

   $ showline < showline
   type line number (0 to stop): 1
   line 1: #!/usr/bin/perl -w
   type line number (0 to stop): 3
   line 3: # showline - read lines from stdin,
   type line number (0 to stop): 20
   line 20: }
   type line number (0 to stop): 21
   no such line
   type line number (0 to stop): 0
   $

-- 
Wybo