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TOML

Tom's Obvious, Minimal Language.

By Tom Preston-Werner.

TOML is like INI, only better.

If it's not working for you, you're not drinking enough whisky.

Be warned, this spec is still changing a lot. Until it's marked as 1.0, you should assume that it is unstable and act accordingly.

Example

# This is a TOML document. Boom.

title = "TOML Example"

[owner]
name = "Tom Preston-Werner"
organization = "GitHub"
bio = "GitHub Cofounder & CEO\nLikes tater tots and beer."
dob = 1979-05-27T07:32:00Z # First class dates? Why not?

[database]
server = "192.168.1.1"
ports = [ 8001, 8001, 8002 ]
connection_max = 5000
enabled = true

[servers]

  # You can indent as you please. Tabs or spaces. TOML don't care.
  [servers.alpha]
  ip = "10.0.0.1"
  dc = "eqdc10"

  [servers.beta]
  ip = "10.0.0.2"
  dc = "eqdc10"

[clients]
data = [ ["gamma", "delta"], [1, 2] ] # just an update to make sure parsers support it

# Line breaks are OK when inside arrays
hosts = [
  "alpha",
  "omega"
]

Spec

TOML is designed to be unambiguous and as simple as possible. There should only be one way to do anything. TOML maps to a simple hash table. TOML is case-sensitive.

Definitions

Whitespace means tab (0x09) or space (0x20).

Comments

Speak your mind with the hash symbol. They go from the symbol to the end of the line.

# I am a comment. Hear me roar. Roar.
key = "value" # Yeah, you can do this.

Primitives

String, Integer, Float, Boolean, Datetime, Array.

Strings are UTF8 surrounded by double quotes. Quotes and other special characters must be escaped.

"I'm a string. \"You can quote me\". Tab \t newline \n you get it."

Here is the list of special characters.

\0 - null character  (0x00)
\t - tab             (0x09)
\n - newline         (0x0a)
\r - carriage return (0x0d)
\" - quote           (0x22)
\\ - backslash       (0x5c)

Integers are bare numbers, all alone. Feeling negative? Do what's natural. 64-bit minimum size expected.

42
-17

Floats are like integers except they have a single dot within. There must be at least one number on each side of the decimal point. 64-bit (double) precision expected.

3.1415
-0.01

Booleans are just the tokens you're used to. Always lowercase.

true
false

Datetimes are ISO8601 dates, but only the full zulu form is allowed.

1979-05-27T07:32:00Z

Arrays are square brackets with other primitives inside. Whitespace is ignored. Elements are separated by commas. No, you can't mix data types, that's stupid.

[ 1, 2, 3 ]
[ "red", "yellow", "green" ]
[ [ 1, 2 ], [3, 4, 5] ]
[ [ 1, 2 ], ["a", "b", "c"] ] # this is ok

Arrays can also be multiline. So in addition to ignoring whitespace, arrays also ignore newlines between the brackets. Terminating commas are ok before the closing bracket.

key = [
  1, 2, 3
]

key = [
  1,
  2, # this is ok
]

That's it. That's all you need, and you're gonna like it.

Hash me

There are two ways to make keys. I call them "key groups" and "keys". Both are just regular keys, but key groups only ever have a single hash as their value.

Key groups appear in square brackets on a line by themselves. You can tell them apart from arrays because arrays are only ever values.

[keygroup]

Under that, and until the next key or EOF are the key/values of that key group. keys are on the left of the equals sign and values are on the right. Keys start with the first non-whitespace character and end with the last non-whitespace character before the equals sign.

[keygroup]
key = "value"

You can indent keys and their values as much as you like. Tabs or spaces. Knock yourself out. Why, you ask? Because you can have nested hashes. Snap.

Nested hashes are denoted by key groups with dots in them. Name your key groups whatever crap you please, just don't use a dot. Dot is reserved. OBEY.

[key.tater]
type = "pug"

In JSON land, that would give you the following structure.

{ "key": { "tater": { "type": "pug" } } }

You don't need to specify all the superkeys if you don't want to. TOML knows how to do it for you.

# [x] you
# [x.y] don't
# [x.y.z] need these
[x.y.z.w] # for this to work

When converted to a hash table, an empty key group should result in the key's value being an empty hash table.

Be careful not to overwrite previous keys. That's dumb. And should produce an error.

# DO NOT WANT
[fruit]
type = "apple"

[fruit.type]
apple = "yes"

Seriously?

Yep.

But why?

Because we need a decent human readable format that maps to a hash and the YAML spec is like 80 pages long and gives me rage. No, JSON doesn't count. You know why.

Oh god, you're right

Yuuuup. Wanna help? Send a pull request. Or write a parser. BE BRAVE.

Implementations

If you have an implementation, send a pull request adding to this list. Please note the commit SHA1 or version tag that your parser supports in your Readme.