add notes to shell script

imagenet/extract_ILSVRC.sh

@@ -29,16 +29,47 @@ mkdir imagenet
 #
 # Extract the training data:
 #
+# Create train directory; move .tar file; change directory
 mkdir imagenet/train && mv ILSVRC2012_img_train.tar imagenet/train/ && cd imagenet/train
+# Extract training set; remove compressed file
 tar -xvf ILSVRC2012_img_train.tar && rm -f ILSVRC2012_img_train.tar
+#
+# At this stage imagenet/train will contain 1000 compressed .tar files, one for each category
+#
+# For each .tar file: 
+#   1. create directory with same name as .tar file
+#   2. extract and copy contents of .tar file into directory
+#   3. remove .tar file
 find . -name "*.tar" | while read NAME ; do mkdir -p "${NAME%.tar}"; tar -xvf "${NAME}" -C "${NAME%.tar}"; rm -f "${NAME}"; done
+#
+# This results in a training directory like so:
+#  imagenet/train/
+#  ├── n01440764
+#  │   ├── n01440764_10026.JPEG
+#  │   ├── n01440764_10027.JPEG
+#  │   ├── ......
+#  ├── ......
+#
+# Change back to original directory
 cd ../..
 #
 # Extract the validation data and move images to subfolders:
 #
-mkdir imagenet/val && mv ILSVRC2012_img_val.tar imagenet/val/ && cd imagenet/val && tar -xvf ILSVRC2012_img_val.tar
+# Create validation directory; move .tar file; change directory; extract validation .tar; remove compressed file
+mkdir imagenet/val && mv ILSVRC2012_img_val.tar imagenet/val/ && cd imagenet/val && tar -xvf ILSVRC2012_img_val.tar && rm -f ILSVRC2012_img_val.tar
+# get script from soumith and run; this script creates all class directories and moves images into corresponding directories
 wget -qO- https://raw.githubusercontent.com/soumith/imagenetloader.torch/master/valprep.sh | bash
 #
+# This resilts in a validation directory like so:
+#
+#  imagenet/val/
+#  ├── n01440764
+#  │   ├── ILSVRC2012_val_00000293.JPEG
+#  │   ├── ILSVRC2012_val_00002138.JPEG
+#  │   ├── ......
+#  ├── ......
+#
+#
 # Check total files after extract
 #
 #  $ find train/ -name "*.JPEG" | wc -l