Re: how to redirect verbose to file?

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On 28Apr2010 20:23, Dave Ihnat <dihnat@xxxxxxxxxx> wrote:
| On Thu, Apr 29, 2010 at 10:59:45AM +1000, Cameron Simpson wrote:
| > Then it is excessive. Drop the "2>&1" and it should _still_ work.
| > As mentioned earlier, this incantation is backwards. Redirections are
| > applied left to right, so "2>&1" probably changes nothing.
| 
| Hm.  Actually, this is very common in Unix/Linux; it indicates
| redirecting the error stream into the stdout stream.  If the messages
| are being generated on the stdout stream, you're right.

The redirection indeed sends stderr to stdout.
BUT...
It _then_ sends stdout to a file, and _do_not_ take stderr with it.

Usually what people want is both streams in the file, done like this:

  >filename 2>&1

"Send stdout to the file, send stderr to where stdout is now going."
Thus both into the file.

The redirection supplied:

  2>&1 >filename

sends stderr to wherever stdout _was_ going, then sends stdout to a
file, leaving stderr _not_ going to the file but to stdout's old
destination.

It boggles my mind that I've seen three separate people recommend
the latter usually-wrong ordering in this thread.

Maybe you're all reading something into the OP's requirements that I
missed?

Observe:

  [/home/cameron]janus*255> cat >>foo.sh
  echo out >&1
  echo err >&2
  [/home/cameron]janus*> sh foo.sh
  out
  err
  [/home/cameron]janus*> sh foo.sh >out 2>&1
  [/home/cameron]janus*> cat out
  out
  err
  [/home/cameron]janus*> sh foo.sh 2>&1 >out
  err
  [/home/cameron]janus*> cat out
  out
  [/home/cameron]janus*> 

Is this unexpected?

Cheers,
-- 
Cameron Simpson <cs@xxxxxxxxxx> DoD#743
http://www.cskk.ezoshosting.com/cs/

Draw little boxes with arrows.  It helps.       - Michael J. Eager

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