On Thursday 08 January 2009 14:13, John McKown wrote:
>Well, shoot. That never even occurred to me. What I thought that would do
>was:
>
>Change stderr to go where stdout currently goes, then change stdout to go
>into the pipe. I based this on the fact that if I do:
>
>command 2>&1 1>x.tmp
>
>Then stderr still comes to my terminal. It does not go to x.tmp. I guess
>there is some special code in bash to recognize the redirection & piping
>as "special".
Actually, there's no special case for this. The rule is that the shell
processes I/O redirections left-to-right. The "2>&1" syntax just means" make
file descriptor 2 (stderr) refer to whatever file descriptor 1 (stdout)
refers to. It doesn't change stdout at all. File descriptor 1 already
refers to the pipe because the shell creates the pipes as it is parsing the
pipeline, before it parses the simple commands within the pipeline.
I hope that makes sense! :-)
- MacK.
-----
Edmund R. MacKenty
Software Architect
Rocket Software
275 Grove Street · Newton, MA 02466-2272 · USA
Tel: +1.617.614.4321
Email: m...@rs.com
Web: www.rocketsoftware.com
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