Hi Datakanja,
I am not entirely sure what you are trying to do, but the arguments
this should not happen
are already separated per default POSIX parsing. You do not need --colsep.
Thus
parallel --dry-run -n 2 echo {} ::: this should not happen
correctly produces on my macbook, with 2 processors:
echo this should
echo not happen
as the maximum number of arguments assigned to echo will be 2, so the first two
arguments are sent to processor 1 and the next two are sent to processor 2.
If you want each processor to echo one argument at a time, then do:
parallel --dry-run -n 1 echo {} ::: this should not happen
which then gives:
echo this
echo should
echo not
echo happen
This is what you want to do right?
I hope this will be helpful.
Best regards,
Lianheng
================================================
Lianheng Tong Tel: +44 79 1758 3822
Room S4.02, Strand Building Fax: +44 20 7848 2420
Department of Physics [email protected]
Kings College London
Strand, London WC2R 2LS, U.K.
================================================
On 6 Jan 2014, at 11:06, ChessDoter wrote:
> Hi Lianheng,
>
> thanks for avoiding calling me PEBE. ;-)
>
> Ok, i do see now, that the ` has to be escaped, like
>
> echo this should not happen | xargs -n 1 echo | parallel --dry-run -n 2 echo
> \`echo {}\`
>
> Would you please provide a pointer to the solution of the --colsep problem? i
> wasnt able to get rid of the xargs step for that on my own.
>
> Best regards
> Datakanja
>
> Am 06.01.2014 11:42, schrieb Lianheng Tong:
>> Hi,
>>
>> I think the problem you have encountered is a problem associated with a
>> possible misunderstanding how POSIX command lines are interpreted by the
>> system, rather than a particular problem with parallel.
>>
>> Best regards,
>>
>> Lianheng
>>
>> ================================================
>> Lianheng Tong Tel: +44 79 1758 3822
>> Room S4.02, Strand Building Fax: +44 20 7848 2420
>> Department of Physics [email protected]
>> <mailto:[email protected]>
>> Kings College London
>> Strand, London WC2R 2LS, U.K.
>> ================================================
>>
>> On 6 Jan 2014, at 10:35, ChessDoter wrote:
>>
>>> hello,
>>>
>>> far from being a power user with linux...
>>>
>>> ... i happen to play with parallel...
>>>
>>> and get confused/surprised at times. Like so:
>>>
>>> echo this should not happen | xargs -n 1 echo | parallel --dry-run -n 2
>>> echo `echo {}`
>>>
>>> First, i was not able to separate the 4 words into different arguments with
>>> --colsep ' ', so that is why i used xargs in the mix.
>>> Then, i did not expect --dry-run to allow for execution of the embedded
>>> `echo` command.
>>>
>>> Ok, i can imagine scenarios, when this comes in handily...
>>>
>>> My current conclusion is: be VERY careful with this powerful tool, test
>>> thoroughly before execution but even then... (can i trust it?) beware of
>>> unexpected side-effects.
>>>
>>> just my 2 cents
