how to pipe to stdout and stderr

how to pipe to stdout and stderr

[Andy Spiegl]

Maybe I'm just too tired right now, but I can't find the solution how to
pipe the standard output and standard error to 2 different programs.

Example:
 program foo   (prints to stdout and stderr)
  program bar1 should receive only stdout
  program bar2 should receive only stderr

How can I do this?  Someone knows how to do that in bash, too?

Thanks so much,
 Andy.

-- 
           http://peru.spiegl.de  Our project
      http://radiomaranon.org.pe  Radio Marañón, Jaén, Perú
                              o      _     _         _
  ------- __o       __o      /\_   _ \\o  (_)\__/o  (_)          -o)
  ----- _`\<,_    _`\<,_    _>(_) (_)/<_    \_| \   _|/' \/       /\\
  ---- (_)/ (_)  (_)/ (_)  (_)        (_)   (_)    (_)'  _\o_    _\_v
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 If you can't write your ideas on the back of my calling card,
 you don't have a clear idea.  -- David Belasco

Re: how to pipe to stdout and stderr

[Ibraheem Umaru-Mohammed]

On Thu, 2003-12-18 at 00:12, Andy Spiegl wrote:
> Maybe I'm just too tired right now, but I can't find the solution how to
> pipe the standard output and standard error to 2 different programs.
> 
> Example:
>  program foo   (prints to stdout and stderr)
>   program bar1 should receive only stdout
>   program bar2 should receive only stderr
> 
> How can I do this?  Someone knows how to do that in bash, too?
[...]
<ibraheem@umarumohammed:~/try> ls
<ibraheem@umarumohammed:~/try> touch foo
<ibraheem@umarumohammed:~/try> ls foo bar
ls: bar: No such file or directory
foo
<ibraheem@umarumohammed:~/try> ls foo bar > stdout 2> stderr
<ibraheem@umarumohammed:~/try> cat stdout 
foo
<ibraheem@umarumohammed:~/try> cat stderr 
ls: bar: No such file or directory
[...]

HTH,

			--ibz.

Re: how to pipe to stdout and stderr

[Andy Spiegl]

> <ibraheem@umarumohammed:~/try> ls foo bar > stdout 2> stderr

Thanks, but I don't want to redirect to 2 files, but pipe to 2 programs.
 Andy.

-- 
           http://peru.spiegl.de  Our project
      http://radiomaranon.org.pe  Radio Marañón, Jaén, Perú
                              o      _     _         _
  ------- __o       __o      /\_   _ \\o  (_)\__/o  (_)          -o)
  ----- _`\<,_    _`\<,_    _>(_) (_)/<_    \_| \   _|/' \/       /\\
  ---- (_)/ (_)  (_)/ (_)  (_)        (_)   (_)    (_)'  _\o_    _\_v
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Ever wonder about those people who spend $2.00 a piece on those little
 bottles of Evian water?  Try spelling Evian backwards: NAIVE
    (George Carlin, US comedian)

Re: how to pipe to stdout and stderr

[Hisham Muhammad]

On Thursday 18 December 2003 00:01, Andy Spiegl wrote:
> > <ibraheem@umarumohammed:~/try> ls foo bar > stdout 2> stderr
>
> Thanks, but I don't want to redirect to 2 files, but pipe to 2 programs.

Use mkfifo, maybe?

hisham@aria ~/test] mkfifo err
hisham@aria ~/test] mkfifo out

hisham@aria ~/test] cat out | tac > out.txt &
hisham@aria ~/test] cat err | tr '[:lower:]' '[:upper:]' > err.txt &
hisham@aria ~/test] ls * zzz > out 2> err

hisham@aria ~/test]cat err.txt
LS: ZZZ: NO SUCH FILE OR DIRECTORY

hisham@aria ~/test] ls -1
err
err.txt
out
out.txt

hisham@aria ~/test] cat out.txt
out.txt
out
err.txt
err

-- 
Hisham Muhammad
"...and this is the first step."

Re: how to pipe to stdout and stderr

[Ibraheem Umaru-Mohammed]

On [18/12/03 03:01 +0100], Andy Spiegl wrote:
> > <ibraheem@umarumohammed:~/try> ls foo bar > stdout 2> stderr
> 
> Thanks, but I don't want to redirect to 2 files, but pipe to 2 programs.
>  Andy.

Right, I get ya. Does this help:

[...]
<ibraheem@umarumohammed:~/try> ls
<ibraheem@umarumohammed:~/try> touch foo
<ibraheem@umarumohammed:~/try> ls
foo
<ibraheem@umarumohammed:~/try> ls foo bar >>(cat > stdout) 2>>(cat > stderr)
<ibraheem@umarumohammed:~/try> ls
foo	stderr	stdout
<ibraheem@umarumohammed:~/try> cat stdout
foo
<ibraheem@umarumohammed:~/try> cat stderr
ls: bar: No such file or directory
[...]


HTH,

			--ibz.
-- 

Re: how to pipe to stdout and stderr

[Dan Nelson]

In the last episode (Dec 18), Andy Spiegl said:
> Maybe I'm just too tired right now, but I can't find the solution how to
> pipe the standard output and standard error to 2 different programs.
> 
> Example:
>  program foo   (prints to stdout and stderr)
>   program bar1 should receive only stdout
>   program bar2 should receive only stderr
> 
> How can I do this?  Someone knows how to do that in bash, too?

It's a little tricky since regular pipes are linear.  Zsh does let you
redirect to commands though:

% ( echo stdout ; echo 1>&2 stderr ) > >(tr a-z A-Z) 2> >(tr a-z b-za)
tuefss
STDOUT
%

See the zsh manpage, under the heading "PROCESS SUBSTITUTION".

-- 
	Dan Nelson
	dnelson@allantgroup.com

Re: how to pipe to stdout and stderr

[Andy Spiegl]

Thanks guys!
 Andy.

-- 
           http://peru.spiegl.de  Our project
      http://radiomaranon.org.pe  Radio Marañón, Jaén, Perú
                              o      _     _         _
  ------- __o       __o      /\_   _ \\o  (_)\__/o  (_)          -o)
  ----- _`\<,_    _`\<,_    _>(_) (_)/<_    \_| \   _|/' \/       /\\
  ---- (_)/ (_)  (_)/ (_)  (_)        (_)   (_)    (_)'  _\o_    _\_v
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 "In a cat's eye, all things belong to cats."  --English proverb