Re: GNU mv and GNU find

[Gabriele Laurenzi]

Hi Bernhard,

Many thanks for your email.

Yours,

Gabriele

On Tue, May 21, 2019 at 8:21 AM Bernhard Voelker
<address@hidden> wrote:
>
> Hi,
>
> it's much better to discuss such things on a mailing list than via direct
> email contact --> therefore I'm adding the GNU findutils mailing list.
>
> (Looking at the easiest solution - see below -, I could've also added the
> GNU coreutils mailing list.)
>
> On 5/17/19 2:32 PM, Gabriele Laurenzi wrote:
> > Adding rms to this email
> >
> > Many thanks again,
> >
> > gl
> >
> > On Fri, May 17, 2019 at 2:31 PM Gabriele Laurenzi
> > <address@hidden> wrote:
> >>
> >> Hello,
> >>
> >> I am Gabriele, and I have a curiosity regarding mv and find, that I
> >> would ask to you (this is not work related; I do also use GNU Linux
> >> for personal use at home).
> >>
> >> At home, I had like 4-5 subdirectories in a directory named
> >> "parent-dir", structure of that fs is as this:
> >>
> >> parent-dir _ dir1
> >>                 _ dir2
> >>                 _ dir3
> >>                 _ dir4
> >>
> >> In dir1, dir2, dir3, dir4 I have respectively something like 1000
> >> files, and 300 of them or so are duplicated (same name, same content,
> >> different indexing) in the directory tree. I made a one liner script
> >> to put all the contents of these four directories in the path above
> >> (../)
> >>
> >> Now, a file manager like for instance Caja (MATE) or alike would have
> >> asked me to replace file x with file y (same name and content) based
> >> on timestamps, but the one-liner I made was like
> >>
> >> find . -type f -mindepth 2 -exec mv -i -- {} . \;
>
> Please use the -mindepth option before any non-option argument (-type).
> You should've got a warning like:
>
>   find: warning: you have specified the -mindepth option after a non-option \
>   argument -type, but options are not positional (-mindepth affects tests  \
>   specified before it as well as those specified after it).  Please specify \
>   options before other arguments.
>
> >> This automatically moves the content of the subdirectories in the
> >> directory "parent-dir". But obviously enough it does replace the file
> >> with the same content and name, so like 40-50 GB of space on disk was
> >> freed.
> >>
> >> I am fine with this, however, I wanted to decide basing on the last
> >> updated file to be saved, in this case I instead got files replaced (I
> >> guess) based on alphabetical order as soon as "find" util did find the
> >> files in the subdirectories.
>
> So you only want to move the file "down" to the current directory if it
> is newer than the one in the destination?  That sounds like you would
> ask for 'mv --update' (or the short -u option of 'mv'):
>
>   $ months='January February March April May'
>
>   $ mkdir $months
>
>   $ for month in $months ; do for day in 1 2 3; do touch --date="${month} 
> ${day}" ${month}/file${day}; done; done
>
>   $ find . -type f -exec ls -log '{}' \;
>   -rw-r--r-- 1 0 Mar  2 00:00 ./March/file2
>   -rw-r--r-- 1 0 Mar  3 00:00 ./March/file3
>   -rw-r--r-- 1 0 Mar  1 00:00 ./March/file1
>   -rw-r--r-- 1 0 Jan  2 00:00 ./January/file2
>   -rw-r--r-- 1 0 Jan  3 00:00 ./January/file3
>   -rw-r--r-- 1 0 Jan  1 00:00 ./January/file1
>   -rw-r--r-- 1 0 Apr  2 00:00 ./April/file2
>   -rw-r--r-- 1 0 Apr  3 00:00 ./April/file3
>   -rw-r--r-- 1 0 Apr  1 00:00 ./April/file1
>   -rw-r--r-- 1 0 Feb  2 00:00 ./February/file2
>   -rw-r--r-- 1 0 Feb  3 00:00 ./February/file3
>   -rw-r--r-- 1 0 Feb  1 00:00 ./February/file1
>   -rw-r--r-- 1 0 May  2 00:00 ./May/file2
>   -rw-r--r-- 1 0 May  3 00:00 ./May/file3
>   -rw-r--r-- 1 0 May  1 00:00 ./May/file1
>
>   $ find . -mindepth 2 -type f -print -exec mv -vu -- '{}' . \;
>   ./March/file2
>   renamed './March/file2' -> './file2'
>   ./March/file3
>   renamed './March/file3' -> './file3'
>   ./March/file1
>   renamed './March/file1' -> './file1'
>   ./January/file2
>   ./January/file3
>   ./January/file1
>   ./April/file2
>   renamed './April/file2' -> './file2'
>   ./April/file3
>   renamed './April/file3' -> './file3'
>   ./April/file1
>   renamed './April/file1' -> './file1'
>   ./February/file2
>   ./February/file3
>   ./February/file1
>   ./May/file2
>   renamed './May/file2' -> './file2'
>   ./May/file3
>   renamed './May/file3' -> './file3'
>   ./May/file1
>   renamed './May/file1' -> './file1'
>
>   $ find . -type f -exec ls -log '{}' \;
>   -rw-r--r-- 1 0 Jan  2 00:00 ./January/file2
>   -rw-r--r-- 1 0 Jan  3 00:00 ./January/file3
>   -rw-r--r-- 1 0 Jan  1 00:00 ./January/file1
>   -rw-r--r-- 1 0 May  2 00:00 ./file2
>   -rw-r--r-- 1 0 May  3 00:00 ./file3
>   -rw-r--r-- 1 0 Feb  2 00:00 ./February/file2
>   -rw-r--r-- 1 0 Feb  3 00:00 ./February/file3
>   -rw-r--r-- 1 0 Feb  1 00:00 ./February/file1
>   -rw-r--r-- 1 0 May  1 00:00 ./file1
>
> I added a -print to 'find' and -v to 'mv' to see what's going on.
> As the January and February directories have processed later, the destination
> file is already newer, and therefore 'mv -u' skips those files.
>
> An alternative to 'mv -u' would be to check explicitly in a shell action
> if the source is newer than the destination:
>
>   $ find . -mindepth 2 -type f \
>       -exec sh -c 'test "$1" -nt "$(basename "$1")" \
>                      && mv -v "$1" . \
>                      || echo "skipping $1"\
>                   ' sh '{}' . \;
>   renamed './March/file2' -> './file2'
>   renamed './March/file3' -> './file3'
>   renamed './March/file1' -> './file1'
>   skipping ./January/file2
>   skipping ./January/file3
>   skipping ./January/file1
>   renamed './April/file2' -> './file2'
>   renamed './April/file3' -> './file3'
>   renamed './April/file1' -> './file1'
>   skipping ./February/file2
>   skipping ./February/file3
>   skipping ./February/file1
>   renamed './May/file2' -> './file2'
>   renamed './May/file3' -> './file3'
>   renamed './May/file1' -> './file1'
>
> Obviously, this is more complex.
>
> >> I did not thought of enabling the -i (interactive flag mode) for find.
>
> I don't understand: there is no -i option for find.
>
> >> I would like to know how find and mv manages a situation like this;
> >> can you answer me?
> >>
> >> Many thanks for Your time and effort in replying to me, it is very 
> >> appreciated.
> >>
> >> Gabriele Laurenzi
>
> Have a nice day,
> Berny