Renaming files randomly

Ruby
1

Got this request yesterday and still haven’t had
time to decipher it and code it – I figured I’d
throw it out here and see what you folks come up with:

Eric wrote:

I want to change the names of several hundred files to random numbers
(without overwriting any files). I have a bunch of pictures for our
reception, but they’re basically in chronological order by their
current
filenames. But I want the slideshow to play in random order, so I
need to
randomize the filenames.

I’ll also ask why the slideshow software can’t just be
told to show things randomly…

Thanks,

2

Hi –

On Mon, 10 Jul 2006, Bil K. wrote:

randomize the filenames.

I’ll also ask why the slideshow software can’t just be
told to show things randomly…

Dir[“photos/*”].sort_by { rand }

If the renaming is really necessary, then something like:

Dir.chdir(“photos”) do
files = Dir["*"]
new_names = [*0…files.size].sort_by { rand }
files.zip(new_names).each do |f,n|
File.rename(f, n.to_s)
end
end

They may not get shown in numerical order, because of how directories
get sorted, but it shouldn’t matter because they’ll be in random order
anyway.

David

3

On Mon, 10 Jul 2006, Bil K. wrote:

randomize the filenames.

I’ll also ask why the slideshow software can’t just be
told to show things randomly…

Thanks,

rather than rename, i’d just make a dir full of links:

harp:~ > cat a.rb
require ‘fileutils’

dir, dir_full_of_links, ignored = ARGV

dir_full_of_links ||= dir + ‘.d.links’
d, f, fu = Dir, File, FileUtils

glob = f.join dir, ‘*’
srcs = d.glob(glob).map{|path| f.expand_path path}

link = ‘a’
dsts = srcs.map{|path| f.join dir_full_of_links, link.succ!}

fu.rm_rf dir_full_of_links
fu.mkdir_p dir_full_of_links
dsts.sort_by{ rand }

srcs.zip(dsts) do |src, dst|
puts “#{ src } -->> #{ dst }”
fu.ln_s src, dst
end

harp:~ > ls -ltar tmp
total 716
-rw-rw-r-- 1 ahoward ahoward 393 May 5 05:30
G2006050506.sfctmp.dat.hdr
-rw-rw-r-- 1 ahoward ahoward 393 May 5 11:30
G2006050512.sfctmp.dat.hdr
-rw-rw-r-- 1 ahoward ahoward 260640 May 5 11:30
G2006050512.sfctmp.dat
-rw-rw-r-- 1 ahoward ahoward 393 May 5 17:30
G2006050518.sfctmp.dat.hdr
-rw-rw-r-- 1 ahoward ahoward 260640 May 5 17:30
G2006050518.sfctmp.dat
-rw-rw-r-- 1 ahoward ahoward 90112 May 23 09:30
G2006050506.sfctmp.dat
drwxrwxr-x 2 ahoward ahoward 8192 Jul 9 09:25 .
drwx------ 170 ahoward ahoward 81920 Jul 9 09:26 …

harp:~ > ruby a.rb tmp
/home/ahoward/tmp/G2006050506.sfctmp.dat -->> tmp.d.links/b
/home/ahoward/tmp/G2006050506.sfctmp.dat.hdr -->> tmp.d.links/c
/home/ahoward/tmp/G2006050512.sfctmp.dat -->> tmp.d.links/d
/home/ahoward/tmp/G2006050512.sfctmp.dat.hdr -->> tmp.d.links/e
/home/ahoward/tmp/G2006050518.sfctmp.dat -->> tmp.d.links/f
/home/ahoward/tmp/G2006050518.sfctmp.dat.hdr -->> tmp.d.links/g

harp:~ > ls -ltar tmp.d.links/
total 88
lrwxrwxrwx 1 ahoward ahoward 44 Jul 9 09:26 g ->
/home/ahoward/tmp/G2006050518.sfctmp.dat.hdr
lrwxrwxrwx 1 ahoward ahoward 40 Jul 9 09:26 f ->
/home/ahoward/tmp/G2006050518.sfctmp.dat
lrwxrwxrwx 1 ahoward ahoward 44 Jul 9 09:26 e ->
/home/ahoward/tmp/G2006050512.sfctmp.dat.hdr
lrwxrwxrwx 1 ahoward ahoward 40 Jul 9 09:26 d ->
/home/ahoward/tmp/G2006050512.sfctmp.dat
lrwxrwxrwx 1 ahoward ahoward 44 Jul 9 09:26 c ->
/home/ahoward/tmp/G2006050506.sfctmp.dat.hdr
lrwxrwxrwx 1 ahoward ahoward 40 Jul 9 09:26 b ->
/home/ahoward/tmp/G2006050506.sfctmp.dat
drwx------ 171 ahoward ahoward 81920 Jul 9 09:26 …
drwxrwxr-x 2 ahoward ahoward 4096 Jul 9 09:26 .

regards.

-a

4

On Mon, 10 Jul 2006 [email protected] wrote:

then the renaming order is

at the end of the loop you’ll have only files ‘a’ and ‘b’ and no error will
have been thrown.

sorry - replace ‘a b c’ with ‘1 2 3’ and ‘c b a’ with ‘3 2 1’ -
basically you
lose data when the slides have numbered names to begin with, which i
noticed
because this is exactly how my slideshow software names it’s slides!
:wink:

-a

5

On Mon, 10 Jul 2006 [email protected] wrote:

end
this loop loses data

if

files = %w( a b c )

and

new_names = %w( c b a )

then the renaming order is

a -->> c
b -->> b
c -->> a

so

File.rename ‘a’, ‘c’ # c is clobbered
File.rename ‘b’, ‘b’ # ok
File.rename ‘c’, ‘a’ # a is clobbered, new c is lost

at the end of the loop you’ll have only files ‘a’ and ‘b’ and no error
will
have been thrown.

regards.

-a

6

[email protected] wrote:

Dir.chdir(“photos”) do
files = Dir["*"]
new_names = [*0…files.size].sort_by { rand }
files.zip(new_names).each do |f,n|
File.rename(f, n.to_s)
end
end

Thanks David.

I’ll push that over and see what comes back.

Also, thanks for showing “zip” in action – I just
learned about that one a couple months ago and hadn’t
figured out a place to use it yet.

Regards,

7

Hi –

On Mon, 10 Jul 2006, [email protected] wrote:

new_names = %w( c b a )
File.rename ‘b’, ‘b’ # ok
File.rename ‘c’, ‘a’ # a is clobbered, new c is lost

at the end of the loop you’ll have only files ‘a’ and ‘b’ and no error will
have been thrown.

sorry - replace ‘a b c’ with ‘1 2 3’ and ‘c b a’ with ‘3 2 1’ - basically you
lose data when the slides have numbered names to begin with, which i noticed
because this is exactly how my slideshow software names it’s slides! :wink:

OK, then:

new_names = [*0…files.size].map {|n| “MUNGED#{n}” }.sort_by { rand
}

:slight_smile:

David

8

On Mon, Jul 10, 2006 at 01:05:06AM +0900, Bil K. wrote:

Thanks David.

I’ll push that over and see what comes back.

Also, thanks for showing “zip” in action – I just
learned about that one a couple months ago and hadn’t
figured out a place to use it yet.

One useful use of zip is transformation two arrays into hash pairs:

Hash[*%w(a b c d).zip([1, 2, 3, 4]).flatten]
=> {“a”=>1, “b”=>2, “c”=>3, “d”=>4}

marcel

9

Hey,

You could rewrite without the zip and the temporary variable…
ala:

Dir.chdir(“photos”) do
Dir["*"].sort_by{rand}.each_with_index do |f,n|
File.rename(f, n.to_s)
end
end

Though be careful, you’ve just lost the file-name extension, and
unpretty things could happen if you run the script over the same
directory multiple times (which I guess could happen when you want to
re-shuffle the playlist).

Regards,

Tris