Bash: Easy backup command

Today I learned a neat trick to create a backup of a file in bash. Instead of typing the file name twice, you can use the following syntax:

cp ./path/to/file.txt{,.bak}

This works by using the shell's brace expansion feature. The command above is equivalent to:

cp ./path/to/file.txt ./path/to/file.txt.bak

You can find out more about expansions in the Bash manual.

Learned this from anthonywritescode