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uxy-format.md

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UXY format

Rationale

UXY format is designed with the following requirements in mind:

  • It should be human-readable.
  • It should be as similar to the output of standard tools, such as ls or ps, as possible.
  • At the same time it should be unambiguous and thus parsable in deterministic manner.
  • It should be, to some minimal extent, self-describing (column names).
  • It should work well with infinite streams (think, for example, the output of tail command).
  • It should be resilient. No possible input should crash the tool.

Records and fields

  • UXY format is a possibly infinite list of lines separated by newlines.
  • Each line is composed of fields separated by arbitrary number of spaces.
  • Fields starting AND ending with a double quote are treated in a special way:
    • The delimiting double-quote characters themselves are ignored.
    • The characters inside the quotes, including spaces, are taken as they are.
    • The only exception are the characters preceded by backslash. These are encoded as follows:
      • \" double quote
      • \\ backslash
      • \a alert (ascii code 0x07)
      • \b backspace (ascii code 0x08)
      • \e escape (ascii code 0x1b)
      • \f formfeed page break (ascii code 0x0c)
      • \n newline (ascii code 0x0a)
      • \r carriage return (ascii code 0x0d)
      • \t horizontal tab (ascii code 0x09)
      • \v vertical tab (ascii code 0x0b)
      • any other escape sequence MUST be interpreted as ? (question mark) character.
  • Any control characters (e.g. TAB) MUST be interpreted as ? (question mark) characters.

Header

  • First line of UXY format is the header.
  • The format of the header line is identical to any other UXY line, however, its semantics differ.
  • The value of a field in the header is the name of that particular column.
  • The spacing of the fields in the header is a hint for the tools. They SHOULD try to align the data with the headers.

Interactions between headers and records

  • Fields may or may not be aligned with each other or with the headers.
  • If there are less fields in a record than in the header the missing values are assumed to be empty strings.
  • It is valid to for a record to have more fields than the header. The tools should consider the name of such column to be an empty string.

Example

NAME  AGE ADDRESS
Alice 25  "Main Road 1, London" "Let's use this unnamed field for comments."
Bob   23  ""
Carol 55  "Hotel \"Excelsior\", New York"
  Dylan             15