Unix Brace Expansion

Brace Expansion allows users to reiterate the same parts of a string without having to type them all out.

Example:

enable_{audio,video}
# generates 'enable_audio' and 'enable_video'

echo a{p,c,d,b}e
# generates 'ape ace ade abe'

echo {a,b,c}{d,e,f}
# generates 'ad ae af bd be bf cd ce cf'

echo a{,b,c}z
# generates 'az abz acz'. Note that empty slots simply generates
# the repeating string alone.

Shorthand for Creating Backup Files

With this, we can easily duplicate files and add .bak to the backup file name with the following:

cp example_file{,.bak}