Charts for any wall
Some sheets are for a pupil or for a player. These are not. They are the ones a household reaches for regardless of what anyone is studying: a brew ratio, a size conversion, a status code, the phase of the Moon.
It is the widest set in the catalogue and the least uniform, and that is deliberate. What the sheets share is a kind of question rather than a subject — something you half know, need exactly, and would rather not unlock a phone to find.
They end up in kitchens, hallways and home offices: wherever the question tends to get asked out loud.
FILE PERMISSIONS
Nine bits in three triads, three special bits — and why r and x on a directory are different powers
![FILENAME EXPANSION: *, ?, […]](/api/img/cmsp2eg3h001q2dpdnyxkt8mu)
FILENAME EXPANSION: *, ?, […]
A leading dot and a slash disappear only in filename expansion: the same pattern “*” is seen by case, but not by expansion itself
HERE-DOCUMENTS
The body reaches the command as a single word, and one quote in the delimiter decides whether it arrives as typed
HTTP STATUS CODES
five classes · twenty codes you meet every day
IFS AND FIELD SPLITTING
Two kinds of delimiter: white ones merge into one, non-white ones each cut on their own — and the same value gives one field or four
LIFE CYCLE MODELS
the same steps arranged five ways: the document, the year, and what one turn of the loop covers
THE MIDI PROTOCOL
one top bit separates status from data, seven commands per channel, and how much time a serial wire actually takes
THE FLAGS OF OPEN()
FIVE flags of creating a file — and why O_CREAT|O_EXCL is not a faster check but a check and a creation joined into one indivisible act
${…}: FOUR MODIFICATIONS
The colon asks about emptiness too: in the column of the empty variable it changes the answer four times out of four, and in the other two columns none
${…}: TRIMMING BY PATTERN
The sign says from which end to cut and doubling it says how much: from the same path the same pair of patterns takes away either one character or fifteen
POSIX SIGNALS
Twenty-seven signals, five default actions — and two that cannot be caught, ignored or blocked
THE ORDER OF REDIRECTIONS
Redirections are done from left to right, and “2>&1” copies where the output points at that very moment: the file first — and it holds two lines; the copy first — one
QUOTING IN THE SHELL
29 characters named by the standard, 4 ways to take the meaning off them — and the 3 characters where double quotes stop
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 CONDITIONS OF TRAP
FIVE conditions from the standard — EXIT and four signals — and three extensions a conformant shell refuses
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
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
BEER STYLES
colour, bitterness and strength of 15 styles from the BJCP 2021 guidelines
COCKTAIL FORMULAS
five templates by ratio, not fixed recipes — millilitres straight from the official IBA recipes
NINE DRINKS
the same coffee, different proportions
HOW MUCH COFFEE TO WATER
six methods · weight, grind, time
ARABICA AND ROBUSTA
two species, six varieties, one difference