Bash tips

• To rename all files in a directory from varies UpPerCase to lowercase:

for FILENAME in *;do mv $FILENAME ${FILENAME,,};done

• To resize canvas of all images in directory:

for FILE in *;do convert $FILE {-gravity center} -background transparent -extent 1024x1024 $FILE;done

• To resize all images with fixed width (or height) and keep ratio:

for FILE in *;do convert $FILE -resize 1024x $FILE;done //fixed width, keep ratio
for FILE in *;do convert $FILE -resize x800 $FILE;done //fixed height, keep ratio
for FILE in *;do convert $FILE -resize 600x600 $FILE;done //fixed height, ratio changed respect by w:h

• To echo all files with splited file name & extension:

for FILE in *;do echo "{'file_name': '${FILE%.*}', 'file_extension': '${FILE##*.}'},";done

To be continued...