MongoDB - Update a field using the value of another field

db.COLLECTION_NAME.updateMany(

{},

[{$set: {

"target_field": "$source_field"

}}]

);

MacOS - List the first few rows of a file in terminal

head -n 120 /path/file.txt 

MacOS - Rename extensions for all files in a folder

 for f in *.png; do 

    mv -- "$f" "${f%.png}.jpg"

done