read: A LINE INTO VARIABLES
The last variable takes the whole rest of the line, inner spaces and all; without -r the backslash disappears, and a line with no final newline gives status 1 — although the variable is already full
THE SELECT STATEMENT
8 clauses in the order you write them — and the order they take effect in
THE UMASK
The file mode creation mask: the nine bits it clears, five arguments that name opposite things — and why umask 022 is not chmod 755
THE UNICODE SPACE
1 114 112 code points in 17 planes: 159 866 characters, 137 468 private, 814 730 free
UUID
thirty-six characters: where the version sits, where the variant sits, and what each of the eight versions is made of
VIDEO CARRIERS
nine formats at true scale — and the frame that kept growing after the carrier stopped
VIDEO FORMATS
who published each standard, when, the names it goes by, and what has to be squeezed
WORD EXPANSION
Four steps in a fixed order — and only two of them can change how many fields reach the command