Bash question - redirect stderr to a variable

[James Mcphee]

Sorry, assign stderr to a variable.

On Tue, Mar 15, 2011 at 1:08 AM, James Mcphee <jmcphe at gmail.com> wrote:

> If you just want to assign stderr to a file and don't care about stdout,
> then the following works.
>
>  $ var="$(cat bah 3>&1 1>&2 2>&3)"
>  $ echo $var
> cat: bah: No such file or directory
>
>
> On Tue, Mar 15, 2011 at 12:54 AM, der.hans <PLUGd at lufthans.com> wrote:
>
>> Am 14. Mar, 2011 schwätzte Bryan O'Neal so:
>>
>> moin moin,
>>
>>
>>  Ok - if I want to direct stranded out, standard error, or both to a
>>>
>>
>> Gotta love stranded out :).
>>
>>
>>  file I can do that. If I want to redirect standard out to a variable
>>> for latter use, I can do that. But how do I redirect standard error to
>>> a variable?
>>>
>>
>> If all else fails, you can redirect STDERR to STDOUT, '2>&1'.
>>
>> If you control whatever's giving the errors you can have it set variables
>> that are used later.
>>
>> As to capturing both to variables without using a temporary file, see the
>> bottom of the following page.
>>
>> http://mywiki.wooledge.org/BashFAQ/002
>>
>> If you can do everything you need for one of them in a subshell, then it
>> is possible.
>>
>> ( exec 3>&1; fred=$( { output=$( ls -d /tmp /ztmp 2>&1 1>&3- ); } 3>&1;
>> echo "{$output}" | sed -re 's,/ztmp (.+),/zztop \1,'; ); echo "<$fred>"
>>
>> ( exec 3>&1; fred=$( { output=$( ls -d /tmp /ztmp 2>&1 1>&3- ); } 3>&1;
>> echo "{$output}" | sed -re 's,/ztmp (.+),/zztop \1,' >&2; ); echo
>> "<$fred>" )
>> {ls: Zugriff auf /zztop nicht möglich: Datei oder Verzeichnis nicht
>> gefunden}
>> </tmp>
>>
>> The sed is just to show that I'm mangling the STDERR output once it's been
>> tossed into a variable.
>>
>> Since $output is in a subshell you can't get to it from the normal shell,
>> but you could call a fx() to handle the data.
>>
>> ( mungestderr() { echo "{$output}" | sed -re 's,/ztmp (.+),/zztop \1,'; };
>> exec 3>&1; fred=$( { output=$( ls -d /tmp /ztmp 2>&1 1>&3- ); } 3>&1;
>> mungestderr "$output" ); echo "<$fred>" )
>> </tmp
>> {ls: Zugriff auf /zztop nicht möglich: Datei oder Verzeichnis nicht
>> gefunden}>
>>
>> ( mungestderr() { echo "{$output}" | sed -re 's,/ztmp (.+),/zztop \1,'
>> >&2; }; exec 3>&1; fred=$( { output=$( ls -d /tmp /ztmp 2>&1 1>&3- ); }
>> >3>&1; mungestderr "$output" ); echo "<$fred>" )
>> {ls: Zugriff auf /zztop nicht möglich: Datei oder Verzeichnis nicht
>> gefunden}
>> </tmp>
>>
>> To keep it clear you might just want to toss it into a file or named pipe.
>>
>> ciao,
>>
>> der.hans
>> --
>> #  http://www.LuftHans.com/        http://www.LuftHans.com/Classes/
>> #  ABLEconf - 2011Apr02 - Free Software for Free Enterprise
>> #  "Backups are irrelevant. Only restorals matter." -- der.hans
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>
>
>
> --
> James McPhee
> jmcphe at gmail.com
>



-- 
James McPhee
jmcphe at gmail.com
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