Tag Archives: mv

CLI

Rename files to reflect modified time while preserving extension

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I’m undergoing a big project of scanning old family scrapbooks. I have two scanners involved, each with their own naming scheme, dumping files of various types (pdf, jpg) into the same folder. I need to have an accurate chronological view of when things were scanned (nothing was scanned at the exact same moment.) At this point the only way to get this information is to sort all the files by modified time,  but no other programs but a file manager look at files this way. I needed a way to rename all the files to reflect their modified time.

I found a couple different ways to do this, but settled on a bash for loop utilizing the stat, sed, and mv commands.

Challenge 1

Capture the extension of the files.

Using sed:

ls <filename> | sed 's/.*\(\..*\)$/\1/'

Challenge 2

Obtain the modified time of your file in an acceptable format. I do this using the stat command.

stat -c %y <filename>

%y is the best option here – it leaves no room for ambiguity. You could also choose %Y so the filenames aren’t so large and don’t contain colons (some systems struggle with this.) The downside do this is you only have to-the-second precision. In my case I had a few files that had the same epoch timestamp, which caused problems. More on how to format this can be found here and here.

Stringing it all together

I wrapped it all up in a bash for loop with appropriate variables. This was my final command, which I ran inside the directory I wanted to modify:

for file in *; do name=$(stat -c %y "$file"); ext=$(echo "$file" | sed 's/.*\(\..*\)$/\1/'); mv -n "$file" "$name$ext"; done

The for loop goes through each file one at a time and assigns it to the $file variable.  I then create the name variable which uses the stat command to obtain a precise date modified timestamp of the file. The ext variable is derived from the filename but only keeps the extension (using sed.) The last step uses mv -n (no clobber mode – don’t overwrite anything) to rename the original file to its date modified timestamp. The result: a directory where each file is named precisely when it was modified – a true chronology of what was scanned irrespective of file extension or which scanner created the file. Success.

CLI

Randomize files in a folder

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I wanted to make a simple slideshow for a cheap Kindle turned photo frame in my office. Windows Movie Maker (free, already installed program) does not have a randomize function when importing photos. I had a lot of photos I wanted imported and I wanted them randomized. Movie Maker doesn’t include subfolders for some dumb reason, so I also needed a way to grab pictures from various directories and put them in a single directory.

My solution (not movie-maker specific) was to use bash combined with find, ln, and mv to get the files exactly how I want them. The process goes as follows:

  1. Create a temporary folder
  2. Use the find command to find files you want
    1. Use -type f argument to find only files (don’t replicate directory structure)
    2. Use the -exec argument to call the ln command to create links to each file found
    3. Use the -s argument of ln to create symbolic links
    4. Use the -b argument of ln to ensure duplicate filenames are not overwritten
  3. Invoke a one line bash command to randomize the filenames of those symbolic links

It worked beautifully. The commands I ended up using were as follows:

mkdir temp
cd temp
find /Pictures/2013/ -type f -exec ln -s -b {} . \;
#repeat for each subfolder as needed, unless you want all folders in which case you can just specify the directory beneath it.
find /Pictures/2014/ -type f -exec ln -s -b {} . \;
find /Pictures/2015/ -type f -exec ln -s -b {} . \;

for i in *.JPG; do mv "$i" "$RANDOM.jpg"; done
#repeat for all permutations. The -b argument of ln creates files with tildes in the extension - don't forget about them.
for i in *.jpg; do mv "$i" "$RANDOM.jpg"; done
for i in *.JPG~; do mv "$i" "$RANDOM.jpg"; done
for i in *.jpg~; do mv "$i" "$RANDOM.jpg"; done

The end result was a directory full of pictures with random filenames, ready to be dropped into any crappy slideshow making software of your choosing 🙂