POSIX SIGNALS

Twenty-seven signals, five default actions — and two that cannot be caught, ignored or blocked

Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.

Three sizes in one archive — from a sheet on the fridge to a poster on the wall.

Formats: A4 · A3 · A2
What you get: Print-ready PDFs, one per size, with every letterform converted to outlines — nothing to install, nothing to shift.
Subject: code · everyone · reference · study

The default action is what happens until the process says otherwise. The letter beside a group names that action; the number on the right is how many signals fall into it.

BLOCKING SIGKILL IS A REQUEST THAT SUCCEEDS

You may ask to block SIGKILL, and the request will succeed: sigprocmask() returns success while the signal stays unblocked. The standard has the system enforce this “without causing an error to be indicated”.

The same request made through sigaction() answers with [EINVAL]. One prohibition, two different answers: one function quietly does not comply, the other loudly refuses.

On the sheet

The default action is what happens until the process says otherwise. The letter beside a group names that action; the number on the right is how many signals fall into it.
Colour carries meaning, but meaning never rests on colour alone — the sheet reads in black and white.
Nothing about how it was made: the sheet carries only what the reader needs.

Printing

Three sizes in the archive: A4 — 210×297 mm, A3 — 297×420 mm, A2 — 420×594 mm.
All text is converted to outlines. No fonts to install, and nothing shifts on another machine.
White background and sparing fills — it prints on a home printer without draining the cartridge.
Margins of at least 10 mm: a home printer cannot print to the edge.
No stroke thinner than 0.3 mm, so nothing disappears in print.

Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 9 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.

POSIX SIGNALS

BLOCKING SIGKILL IS A REQUEST THAT SUCCEEDS

On the sheet

Printing

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