framing.md

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Solutions to the Framing Problem

Oil is a shell that lets you write correct programs. Programs often parse multiple records or strings sent over a pipe, i.e. the "framing problem". (This terminology is borrowed from network engineering.)

Oil provides a few solutions for that, and each solution is useful in certain contexts.

Delimiter Based Solutions

Newline as Delimiter

The traditional Unix solution. It doesn't work when the payload contains newlines.

Note that Unix filenames, argv entries, and environ entries can all contain newlines, but not NUL (\0).

NUL as delimiter: read -0

So naturally we also support the the format that find -print0 emits, and xargs -0 consumes.

Solutions That Can Express Arbitrary Bytes

Quoting / Escaping Special characters: QSN

QSN uses backslash escapes like \n, \x00, and \u{3bc} to express arbitrary bytes (and characters).

Length-Prefixed: Netstrings

TODO: Implement this.

Like QSN, this format is "8-bit clean", but:

• A netstring encoder is easier to write than a QSN encoder. This may be useful if you don't have a library handy.
• It's more efficient to decode, in theory.

However, the encoded output may contain binary data, which is hard to view in a terminal.