Bash question - redirect stderr to a variable

[Ben Trussell]

This might be helpful (and by that I mean mostly not helpful - you can
easily send stderr to a file then input a file into a variable
however).

http://stackoverflow.com/questions/962255/redirecting-stderr-to-a-variable-in-a-bash-script

Ben

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