From: Robert Klemme <shortcutter@...>
Date: 2008-08-13T15:42:32+09:00
Subject: Re: File redirects in Ruby? Was Re: Sigh! I'm depressed. Debian vs   Rubyand the backtick and subshells

On 12.08.2008 22:55, John Carter wrote:

> Anyone have a short and easy Ruby way of doing file redirects?

Well, define it once and include it in all scripts where you need it. 
For example:

robert@fussel /cygdrive/c/Temp
$ ./redir.rb
Done #<Process::Status: pid=5384,exited(0)>
Done #<Process::Status: pid=5464,exited(2)>

robert@fussel /cygdrive/c/Temp
$ cat output
drwx------+ 5 robert Kein 0 Aug 13 08:42 .

robert@fussel /cygdrive/c/Temp
$ cat output2
ls: cannot access does_not_exis: No such file or directory
drwx------+ 5 robert Kein 0 Aug 13 08:42 .

robert@fussel /cygdrive/c/Temp
$ cat redir.rb
#!/bin/env ruby

module Kernel
private
   def system_redir(args, fout = ::STDOUT, ferr = ::STDERR, fin = ::STDIN)
     child = fork do
       redir_fd ::STDIN, fin, "r"
       redir_fd ::STDOUT, fout, "w"
       redir_fd ::STDERR, ferr, "w"
       exec *args
     end
     Process.wait2(child).last
   end

   def redir_fd(io, target, mode = nil)
     case target
     when String
       io.reopen(File.open(target, mode))
     when IO
       io.reopen target
     when io
       # do nothing
     when nil
       io.close
     else
       raise ArgumentError, "Invalid target argument #{target.inspect}"
     end
   end
end

res = system_redir %w{ls -ld}, "output"
printf "Done %p\n", res

File.open "output2", "w" do |io|
   res = system_redir %w{ls -ld . does_not_exis}, io, io
   printf "Done %p\n", res
end

robert@fussel /cygdrive/c/Temp


Kind regards

	robert