From: Ronald Fischer <ronald.fischer@...>
Date: 2007-07-02T18:00:56+09:00
Subject: Re: Feature Request: Special file '-' denoting stdin/stdout


> It should be mentioned that both File.new and File.open are
> able to receive file descriptors:

This does not help much, because still I would then need to decide
at runtime, whether (for example) the number 1 passed via the command
line of my program, denotes the file descriptor 1 (stdout) or a file
name "1".

> If you insist on using "-", you might want to have a look on
> either of the implementations below.

Both implementations are fine, but I never doubted that we can
implement this explicitly per application. My point was that this
usage of the "-" has become so common - perhaps because it is 
heavily used in the Gnu world and is built into Perl as well. As
an example for how it works with the Gnu tools, I present a sketch
of a bash script:

  #!/usr/bin/bash
  # This is file exa1.sh
  ...
  fgrep "$1" /var/mail/log $HOME/mailbox $2
  ...

I have several ways to call it, for example

  exa1.sh foo  # search in /var/mail/log and mailbox
  exa1.sh bar mailbox.old  # search also in mailbox.old
  genmail | exa1.sh baz - # also search in the stdout of genmail

Similar in Perl: If you write

  open(RCFILE,$ARGV[3])  # This is Perl

the user can supply on the command line a dash, and the program
would automatically read stdin for RCFILE.

Since this is such a common usage of the '-', I suggest that
it should be incorporated into Ruby in a similar way as in Perl.

Ronald
-- 
Ronald Fischer <ronald.fischer@venyon.com>
Phone: +49-89-452133-162