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I was wondering what would be the most concise way of sorting files by date and then copying every other to a new folder.

My problem: I've got files renamed such that they are called

file1 (101)
file2 (103)
file3 (110)
.
.
.

where the numbering is not indicative of the intrinsic file difference. The only thing that's really different between the two file types I want to sort is their alternating creation date, therefore my rather convoluted above problem statement.

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    To sort the files by date you can use ls -t "-t sort by modification time, newest first". What do you mean with "copying every other"? PS> Do not parse the output of ls you can incur in problems. – Hastur Jan 20 '16 at 14:40
  • Thanks for that already! After sorting I want to copy every other file to a new folder, meaning that I take the first file, copy it, skip the second file, take the third one, copy it, skip the fourth and so on. – lhcgeneva Jan 20 '16 at 14:44
  • Have you considered that if someone (human or program) touches (or added) a file you will get a mess... :-) Even that if you generate(d) or copied those files really fast, they can be modified (=closed) in an asynchronous way? ... [Think weird because it sadly happens each day]. – Hastur Jan 20 '16 at 14:50
  • :D good point! Initially the files were named properly so I could distinguish the two 'classes' of files by name. Then I batch renamed on windows, as I assumed it would work similar to MacOs' finder. Not a good idea because it made 1600 files of the exact same name, only adding a number at the very end. Only thing I know is that the two file classes were created alternatingly. – lhcgeneva Jan 20 '16 at 14:56
  • Start again from the original files, if you can. You can do some tests maybe, but you cannot seriously work if you are not sure 100% about the data. Which kind of results will you obtain? Note that when you proceed lossy, relying on the sureness that a major failure will warn you if something is not correct... the Murphy's_law will show. If those files are of a different kind (check with file file1 file2) you can rely a little more. You can wipe out the doubts with md5sum on local and original copy... – Hastur Jan 20 '16 at 15:05
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The following script seems to be a good one but it will work only if you have "well behaving" filenames [1]:

#!/bin/bash
foo=0
for f in $(ls -rt) ; do 
  if [ $((foo%2)) -eq 0 ];
    then
       echo "even " "$f";  // maybe here copy
    else
       echo "odd" "$f" ;   // maybe here skip
  fi
  let foo++
done

So essentially no newlines, no tab, no spaces... as it seems in your case.
Please remember that is not safe to parse the output of ls [1] and doublecheck always.

If you are not in the safe area in which you can use ls, then you may consider to find a solution with find, maybe taking some inspiration from Gilles' answer [2].


Ps> In case of data corruption, even in a light case as yours, it always needed to check that the patch worked. Often is more convenient to start again from the beginning. If, as I guess, the data size is huge and you cannot transfer/download it again, it's always possible to do some check (e.g. md5sum[3]) on the original data and the patched one.

  • That's pretty much exactly what I was looking for. – lhcgeneva Jan 20 '16 at 15:58
  • I knew but remember,remember,remember all the warning. :) – Hastur Jan 20 '16 at 16:47

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