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THE UMASK

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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

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.

StandardUS$1.50

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Payment and email are handled by Paddle. The download link arrives by email — no account, no password.

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 · memo · study

Read from top to bottom: what the program asks for, what the mask clears, what the file is left with. A mask adds no bit at all, which is why no mask will ever produce an execute bit.

THE OCTAL FORM AND THE SYMBOLIC FORM SAY OPPOSITE THINGS

umask 022 and umask u=rwx,g=rx,o=rx set the very same mask while naming opposite things: the octal argument names the bits taken away, the symbolic one names those left.

The standard defines the symbolic form as a logical complement — which is why a plus in a umask argument gives a permission back and a minus takes one away, the opposite of chmod.

On the sheet

  • Read from top to bottom: what the program asks for, what the mask clears, what the file is left with. A mask adds no bit at all, which is why no mask will ever produce an execute bit.
  • 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.

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