RE: Advanced Korn Question

On Tue, 13 Mar 2001, hp wrote:

> can you tell mne what the difference is between:
> > $log 2>&1 &
> and
> 2>&1 > $log &
>
> if tried both ways and the std err and std out go to the log both ways.
>

Probably not, unless you have some strange variant of ksh.

When you redirect STDOUT with "> $log", STDOUT is no longer pointing to file descriptor 1, it is pointing to some new file descriptor.

Here's what happens when you redirect STDERR first:

  date -%sdfd 2>&1 >|date.txt

STDERR is redirected to STDOUT, which is file descriptor number 1. STDOUT is then redirected to some new file descriptor. STDERR from this command will not appear in the file "date.txt", but rather will appear on the screen, which is still file descriptor 1. Try it.

Now change it to this:

  date -%sdfd >|date.txt 2>&1

Now STDOUT is redirected first, and it is sent to some new file descriptor. When STDERR is next redirected, it will point at the new file descriptor for STDOUT, and the error output will appear in the file.

Jared

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