Redirect stderr and not stdout?

[Andrew Lee]

Is it possible to redirect stderr and not stdout?

Thanks.

Andrew

[Tony Porczyk]

kl...@hmc.edu (Andrew Lee) writes:

>Is it possible to redirect stderr and not stdout?

Your fingerd does not show which shell you are using, so I can only
advise you to use an sh-like shell (sh, ksh, bash, etc), not the
csh-like shell (csh, tcsh). Try "man ksh" or "man bash" or "man sh".
There should be examples on how to do it.

t.
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Tony Porczyk * tpor...@infobound.com * San Jose, California
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[Pete Houston]

Andrew Lee <kl...@hmc.edu> wrote in comp.unix.shell:
#Is it possible to redirect stderr and not stdout?

Yes. To send stderr to file log and not stdout do

foo 2> log

where foo is your command producing output & error. Naturally this will
will not work for csh-type shells.

Pete

[Brian S Hiles]

Andrew Lee (kl...@hmc.edu) wrote:
: Is it possible to redirect stderr and not stdout?
: Andrew

in t/csh: from "Csh Programming Considered Harmful" by Tom Christensen:

1. FILE DESCRIPTORS

The most common problem encountered in csh programming is that
you can't do file-descriptor manipulation. All you are able to
do is redirect stdin, or stdout, or dup stderr into stdout.
Bourne-compatible shells offer you an abundance of more exotic
possibilities.

1a. Writing Files

In the Bourne shell, you can open or dup arbitrary file descriptors.
For example,

exec 2>errs.out

means that from then on, stderr goes into errs file.

Or what if you just want to throw away stderr and leave stdout
alone? Pretty simple operation, eh?

cmd 2>/dev/null

Works in the Bourne shell. In the csh, you can only make a pitiful
attempt like this:

(cmd > /dev/tty) >& /dev/null

But who said that stdout was my tty? So it's wrong. This simple
operation *CANNOT BE DONE* in the csh.

Along these same lines, you can't direct error messages in csh scripts
out stderr as is considered proper. In the Bourne shell, you might say:

echo "$0: cannot find $file" 1>&2

but in the csh, you can't redirect stdout out stderr, so you end
up doing something silly like this:

sh -c 'echo "$0: cannot find $file" 1>&2'
--

In k/sh or bash:

command 2>file.stderr

"2" means file descriptor two (well, acually: _file unit number_ two) which
refers to standard error.

-Brian
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[Stewart Ravenhall]

Tony Porczyk <tpor...@best.com> wrote in article
<tporczyk.855186497@shellx>...

> kl...@hmc.edu (Andrew Lee) writes:
>
> >Is it possible to redirect stderr and not stdout?
>

> Your fingerd does not show which shell you are using, so I can only
> advise you to use an sh-like shell (sh, ksh, bash, etc), not the
> csh-like shell (csh, tcsh).

If you are using csh you can redirect stderr and stdout to different places
using
(command > outfile) >& errorfile

But (as Tony pointed out) using other shells is better!

Cheers,
Stewart.