RE: Processing files from a tar archive in parallel

[Cook, Malcolm]

Hmmm

use tar-t to extract the filenames pipe that into parallel to call tar again to 
extract just that file and pipe it to some other command

tar -t big-file.tar.gz  | parallel tar -f big-file.tar.gz - '|' 
someCommandThatReadsFromStdIn

Malcolm Cook
Stowers Institute for Medical Research -  Bioinformatics
Kansas City, Missouri  USA
 
 

> -----Original Message-----
> From: parallel-bounces+mec=stowers.org@gnu.org 
> [mailto:parallel-bounces+mec=stowers.org@gnu.org] On Behalf 
> Of Ole Tange
> Sent: Tuesday, March 29, 2011 4:14 PM
> To: Jay Hacker
> Cc: parallel@gnu.org
> Subject: Re: Processing files from a tar archive in parallel
> 
> On Tue, Mar 29, 2011 at 10:14 PM, Jay Hacker 
> <jayqhacker@gmail.com> wrote:
> > On Tue, Mar 29, 2011 at 11:20 AM, Hans Schou <chlor@schou.dk> wrote:
> >> On Tue, 29 Mar 2011, Jay Hacker wrote:
> >>
> >>> I have a large gzipped tar archive containing many small 
> files; just 
> >>> untarring it takes a lot of time and space.  I'd like to 
> be able to 
> >>> process each file in the archive, ideally without untarring the 
> >>> whole thing first,
> :
> >> tar xvf big-file.tar.gz | parallel echo "Proc this file {}"
> >>
> >> Parallel will start when the first file is untared.
> :
> > That is a great idea.  However, can I be sure the file is 
> completely 
> > written to disk before tar prints the filename?
> 
> While I loved Hans' idea, it does indeed have a race 
> condition. This should run 'ls -l' on each file after 
> decompressing and clearly fails now and then:
> 
> $ tar xvf ../i.tgz | parallel ls -l > ls-l
> ls: cannot access 1792: No such file or directory
> ls: cannot access 209: No such file or directory
> ls: cannot access 21: No such file or directory
> ls: cannot access 2256: No such file or directory
> ls: cannot access 2349: No such file or directory
> ls: cannot access 2363: No such file or directory
> ls: cannot access 246: No such file or directory
> ls: cannot access 2712: No such file or directory
> 
> But you could unpack in a new dir and use:
> http://www.gnu.org/software/parallel/man.html#example__gnu_par
> allel_as_dir_processor
> 
> That seems to work.
> 
> /Ole
> 
>