Words, quotes, and arguments

The idea

These lessons use Bash 5, not a generic POSIX shell. A command receives arguments after Bash parses words and performs expansions. Spaces in the source separate words unless quoting protects them. Single quotes preserve literal characters; double quotes allow parameter expansion while preventing ordinary word splitting and filename expansion of the result. Quoting is therefore part of preserving a value’s structure.

Store one piece of data in a variable and expand it as a quoted argument. Prefer a fixed printf format with data supplied separately, so percent signs inside input are not interpreted as formatting instructions. Do not build a command as one string and expect quoting inside that string to be reparsed safely. Arrays and explicit arguments provide a clearer foundation for later automation.

#!/usr/bin/env bash
name="Ada Lovelace"
printf 'Hello, %s\n' "$name"
printf '%s\n' '$name'

Hello, Ada Lovelace
$name

Double quotes expand name as one argument. Single quotes preserve the literal dollar sign and variable name in the second command.