From: Robert Klemme <bob.news@...>
Date: 2003-12-16T18:51:55+09:00
Subject: Re: redirect stdout for Kernel.system()?


You can use IO.popen for that:
http://whytheluckystiff.net/ruby/pickaxe/html/ref_c_io.html#IO.popen

    robert

"Neil Spring" <nspring@cs.washington.edu> schrieb im Newsbeitrag
news:20031216065336.GA14158@cs.washington.edu...
> I'd like to be able to say:
>
>   $stdout=File.open("foo.out", "w")
>   Kernel.system("/bin/echo", "foo")
>
> intead of:
>
>   Kernel.system("/bin/echo foo > foo.out")
>
> which requires two processes; forking a "/bin/sh" for
> something as simple as redirection is sad.
>
> In ruby1.6.8, this works. In ruby1.8.1 and current cvs, the
> behavior is to redirect puts output to the file (yay!), but
> the stdout of the child process is not affected (boo.).
>
> I think it is valuable to have the output of system() go to
> the currently defined $stdout.  From before I found ruby,
> perl will allow 'open(STDOUT, ">ick.out"); system("/bin/echo
> perl is icky")'.
>
> Is this a bug, intended behavior, or known ambiguity?
> Is there an alternative method I haven't thought of?
>
> (test process output follows, maybe it's just me.)
>
> thanks,
> -neil
>
>
> (in the output below, the duplicated messages are probably
> due to buffering during the fork)
>
> rf:/tmp> cat ~/foo.rb
> #!/usr/bin/ruby
>
> $stdout=File.open("foo.out", "w")
> puts "fooble"
> Kernel.system("echo", "foo")
>
> Thread.new {
>   $stdout=File.open("bar.out", "w")
>   puts "barble"
>   Kernel.system("echo", "bar")
> }.join
>
> Process.fork {
>   $stdout=File.open("baz.out", "w")
>   puts "bazzle"
>   Kernel.system("echo", "baz")
> }
> Process.wait
>
> rf:/tmp> rm *.out
>
> rf:/tmp> ruby1.8 ~/foo.rb
> foo
> bar
> baz
>
> rf:/tmp> cat baz.out
> bazzle
>
> rf:/tmp> cat bar.out
> barble
> barble
>
> rf:/tmp> cat foo.out
> fooble
> fooble
>
> rf:/tmp> ruby1.8 --version
> ruby 1.8.1 (2003-11-11) [i386-linux]
>
> rf:/tmp> ruby --version
> ruby 1.6.8 (2003-07-09) [i386-linux]
>
> rf:/tmp> rm *.out
>
> rf:/tmp> ruby ~/foo.rb
>
> rf:/tmp> cat *.out
> barble
> bar
> bazzle
> baz
> fooble
> foo
>
>
>