Getting text through unchanged.
WHY QUOTING EXISTS
To stop the shell interpreting characters you want passed literally.
WHAT DOUBLE QUOTES DO
Prevent wildcard expansion and word splitting, while still expanding variables.
WHAT SINGLE QUOTES DO
Prevent everything, including variable expansion.
WHAT A BACKSLASH DOES
Escapes the next character only.
WHAT TO USE FOR A PATH WITH SPACES
Double quotes, or escape each space.
WHY UNQUOTED VARIABLES ARE THE COMMONEST SCRIPT BUG
A value containing a space becomes two arguments, and an empty value disappears entirely.
WHAT THAT CAUSES IN A DELETION
The command acts on the wrong thing, or on everything.
WHAT THE RULE IS
Quote every variable, always, unless you have a specific reason not to.
WHAT COMMAND SUBSTITUTION IS
Running a command and using its output as text.
WHAT FORM TO PREFER
Dollar sign and parentheses, rather than backticks.
WHY
It nests, and it is far easier to read.
WHAT TO QUOTE IT WITH
Double quotes, to preserve the output intact.
WHAT TO BE CAREFUL WITH
Passwords containing special characters Filenames containing spaces, quotes or newlines
WHAT TO DO ABOUT AWKWARD FILENAMES
Handle them with find and null separators rather than parsing listings.
