Values

Values: Quotes: Double, Single and None, Values from Commands: $( ) and $(( )).

Updated November 10, 2026

1. Quotes: Double, Single and None (Journeyman): Without quotes, the shell splits a variable's value at its spaces and turns a * into file names, the number-one bash bug; "$name" in double quotes keeps the value exactly as it is, and single quotes keep everything as typed.
2. Values from Commands: $( ) and $(( )) (Apprentice): $( ) runs a command and puts what it prints into another command or a variable, such as today's date in a backup's name, and $(( )) works out whole-number arithmetic, such as an age or a count plus one.