bash script? how to rename files in random way?

lefty.crupps · 05-10-2006, 09:48 PM

I have a lot of photos that I need to put into a random-order slideshow. Easiest would be to just drag-and-drop the whole lot. Is there any way to scan a directory and batch-rename a group of files into random names, but keeping the extension? (.jpg in this case)

jlinkels · 05-10-2006, 10:19 PM

Something like:

Code:

for fname in *.jpg
do
   mv fname $RANDOM.jpg
done

If you want something more sophisticated use the rename command.

rename s/oldpart_of_filename.jpg/newname.jpg/ oldfile.jpg

http://www.faqs.org/docs/abs/HTML/

jlinkels

PS. I shouodl not have taken taht asty irish Coffee but I hope I gave somathing ti rename files adn not to delterr them all.

lefty.crupps · 05-21-2006, 09:32 PM

thanks jlinkels, but how do i use this code? I have created a file called ranren.sh and have tried running

Code:

lefty@1[photo_randomized]$ ./ranren.sh
mv: cannot stat `fname': No such file or directory
mv: cannot stat `fname': No such file or directory
mv: cannot stat `fname': No such file or directory
lefty@1[photo_randomized]$

As you can see, it won't accept "fname" as a file name. What should I change in the script? How would I cycle through each file name (160 total) and give it a random name? (preferably in a subfolder) Many of the files are photo_0001.jpg photo_0002.jpg but others have different names and need to be randomized as well.

thanks for any more help/advice!

p.s. I tried

Code:

ls | mv * $RANDOM.jpg

but it wouldn't move multiple files anywhere except to a directory

homey · 05-21-2006, 10:32 PM

jlinkels forgot to put the $ before fname like this.... $fname. I also put it inside quotes to help with file names that have spaces in them like ---- my latest pic.jpg ----
Also, it's good to have backups in case your code is goofy

and wouldn't hurt to put an echo before the mv command to give it a test run. Then, remove the echo when it looks good.

So, the code may look like this

Code:

for fname in *.jpg
do
   echo mv "$fname" $RANDOM.jpg
done

jlinkels · 05-21-2006, 10:49 PM

Thanks homey, and you are right about the quotes. And the backups of course.

jlinkels

lefty.crupps · 05-21-2006, 10:58 PM

that worked! (but I had to run the script twice to affect all of the files-- only the first 119 changed the first round??)

Thank you both for the help and quick responses!

lefty.crupps

tawan · 08-06-2009, 11:06 PM

hi, using the above

Code:

for fname in *.jpg
do
   echo mv "$fname" $RANDOM.jpg
done

files go missing as I guess the same random number is generated more than once.

I have no fix.

JulianTosh · 08-07-2009, 12:30 AM

No more filename collisions...

for fname in *.jpg;
do
mv "$fname" $(echo "$fname" | sha1sum | cut -f1 -d' ').jpg
done

tawan · 08-07-2009, 12:39 AM

Quote:

Originally Posted by Admiral Beotch

No more filename collisions...

indeed! great.

nbritton · 06-11-2013, 07:24 PM

Quote:

for fname in *.jpg; do

mv "$fname" $(echo "$fname" | sha1sum | cut -f1 -d' ').jpg;

done

That doesn't work on Mac OS X, md5 is a better choice due to ubiquity. The bash one liner below should work on most platforms. It's also worth noting that both of our solutions are only pseudo random...

Code:

for i in *.jpg; do mv $i $(echo $i | md5).jpg; done

If you need more randomness or uniqueness, one way is with openssl:

Code:

for i in *.jpg; do mv $i $(openssl rand -rand $i -hex 16).jpg; done

The length of the random filename is controlled by the "-hex #" switch, it can be set to any length. Each image is used as the seed for each rename operation, for all intents and purposes this should guarantee truly random behavior, provided you don't have duplicate images.

ephesus · 06-07-2014, 09:24 AM

You should probably note that if all of the pseudo-random numbers happen to be the same, you're going to lose all of your files except for the last one.

jlinkels · 06-07-2014, 10:29 AM

Quote:

Originally Posted by ephesus

You should probably note that if all of the pseudo-random numbers happen to be the same, you're going to lose all of your files except for the last one.

You should read the complete thread before posting.

jlinkels

ephesus · 06-07-2014, 12:16 PM

I only see 11 posts, am I missing something? Hashes don't guarantee no collisions.

jlinkels · 06-07-2014, 01:52 PM

Nice try.

First you were talking about all pseudo random numbers be the same so all files would be overwritten with the next. Now it was already a low probability that two random numbers are the same. However it was a significant probability, but for two or a few numbers be the same. Not for all numbers being the same.

Now you have read the thread and you see a hash was proposed as a solution. And you say that the hash might be the same for different pictures. Sure. The probability is like 1.5 x 10E-29 for a md5 sum collision.

Now please state your better solution.

jlinkels

jpollard · 06-08-2014, 09:13 AM

Quote:

Originally Posted by JulianTosh

No more filename collisions...

Code:

for fname in *.jpg;
do
  mv "$fname" $(echo "$fname" | sha1sum | cut -f1 -d' ').jpg
done

A simpler fix is:

Code:

for fname in *.jpg
do
   mv $fname ${RANDOM}_${fname}.jpg
done

The only difference is that if the same random number comes up, then the two pictures will be together.

This also has the benefit of still being able to identify the original name for the image.