| 1 | ---
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| 2 | title: Builtin Functions (Oils Reference)
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| 3 | all_docs_url: ..
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| 4 | body_css_class: width40
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| 5 | default_highlighter: oils-sh
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| 6 | preserve_anchor_case: yes
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| 7 | ---
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| 8 |
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| 9 | <div class="doc-ref-header">
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| 10 |
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| 11 | [Oils Reference](index.html) —
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| 12 | Chapter **Builtin Functions**
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| 13 |
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| 14 | </div>
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| 15 |
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| 16 | This chapter describes builtin functions (as opposed to [builtin
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| 17 | commands](chap-builtin-cmd.html).)
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| 18 |
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| 19 | <span class="in-progress">(in progress)</span>
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| 20 |
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| 21 | <div id="dense-toc">
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| 22 | </div>
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| 23 |
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| 24 | ## Values
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| 25 |
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| 26 | ### len()
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| 27 |
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| 28 | Returns the
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| 29 |
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| 30 | - number of entries in a `List`
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| 31 | - number of pairs in a `Dict`
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| 32 | - number of bytes in a `Str`
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| 33 | - TODO: `countRunes()` can return the number of UTF-8 encoded code points.
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| 34 |
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| 35 | ### func/type()
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| 36 |
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| 37 | Given an arbitrary value, returns a string representing the value's runtime
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| 38 | type.
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| 39 |
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| 40 | For example:
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| 41 |
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| 42 | var d = {'foo': 'bar'}
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| 43 | var n = 42
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| 44 |
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| 45 | = type(d) # => (Str) 'Dict'
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| 46 | = type(n) # => (Str) 'Int'
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| 47 |
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| 48 | Similar names: [type][]
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| 49 |
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| 50 | [type]: chap-index.html#type
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| 51 |
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| 52 |
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| 53 | ## Conversions
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| 54 |
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| 55 | ### bool()
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| 56 |
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| 57 | Returns the truth value of its argument. Similar to `bool()` in python, it
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| 58 | returns `false` for:
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| 59 |
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| 60 | - `false`, `0`, `0.0`, `''`, `{}`, `[]`, and `null`.
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| 61 |
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| 62 | Returns `true` for all other values.
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| 63 |
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| 64 | ### int()
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| 65 |
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| 66 | Given a float, returns the largest integer that is less than its argument (i.e. `floor()`).
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| 67 |
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| 68 | = int(1.99) # => (Int) 1
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| 69 |
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| 70 | Given a string, `Int()` will attempt to convert the string to a base-10
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| 71 | integer.
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| 72 |
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| 73 | = int('10') # => (Int) 10
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| 74 |
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| 75 | <!-- TODO
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| 76 | The base can be overridden by calling with a second argument.
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| 77 | = int('10', base=2) # => (Int) 2
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| 78 | -->
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| 79 |
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| 80 | ```raw
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| 81 | = int('not_an_integer') # fails with an expression error
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| 82 | ```
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| 83 |
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| 84 | ### float()
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| 85 |
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| 86 | Given an integer, returns the corresponding floating point representation.
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| 87 |
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| 88 | = float(1) # => (Float) 1.0
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| 89 |
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| 90 | Given a string, `Float()` will attempt to convert the string to float.
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| 91 |
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| 92 | = float('1.23') # => (Float) 1.23
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| 93 |
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| 94 | ```raw
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| 95 | = float('bar') # fails with an expression error
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| 96 | ```
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| 97 |
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| 98 | ### str()
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| 99 |
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| 100 | Converts a `Float` or `Int` to a string.
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| 101 |
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| 102 | ### list()
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| 103 |
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| 104 | Given a list, returns a shallow copy of the original.
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| 105 |
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| 106 | = list({'a': 1, 'b': 2}) # => (List) ['a', 'b']
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| 107 |
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| 108 | Given an iterable value (e.g. a range or dictionary), returns a list containing
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| 109 | one element for each item in the original collection.
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| 110 |
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| 111 | = list(1 ..= 5) # => (List) [1, 2, 3, 4, 5]
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| 112 |
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| 113 | ### dict()
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| 114 |
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| 115 | Given a dictionary, returns a shallow copy of the original.
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| 116 |
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| 117 | ### runes()
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| 118 |
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| 119 | TODO
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| 120 |
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| 121 | Given a string, decodes UTF-8 into a List of integer "runes" (aka code points).
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| 122 |
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| 123 | Each rune is in the range `U+0` to `U+110000`, and **excludes** the surrogate
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| 124 | range.
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| 125 |
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| 126 | ```raw
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| 127 | runes(s, start=-1, end=-1)
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| 128 | ```
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| 129 |
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| 130 | TODO: How do we signal errors?
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| 131 |
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| 132 | (`runes()` can be used to implement implemented Python's `ord()`.)
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| 133 |
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| 134 | ### encodeRunes()
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| 135 |
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| 136 | TODO
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| 137 |
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| 138 | Given a List of integer "runes" (aka code points), return a string.
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| 139 |
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| 140 | (`encodeRunes()` can be used to implement implemented Python's `chr()`.)
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| 141 |
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| 142 | ### bytes()
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| 143 |
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| 144 | TODO
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| 145 |
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| 146 | Given a string, return a List of integer byte values.
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| 147 |
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| 148 | Each byte is in the range 0 to 255.
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| 149 |
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| 150 | ### encodeBytes()
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| 151 |
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| 152 | TODO
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| 153 |
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| 154 | Given a List of integer byte values, return a string.
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| 155 |
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| 156 | ## Str
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| 157 |
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| 158 | ### strcmp()
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| 159 |
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| 160 | Compare 2 strings, using lexicographic order on bytes.
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| 161 |
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| 162 | Returns 0 if the strings are equal:
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| 163 |
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| 164 | = strcmp('z', 'z') # => (Int) 0
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| 165 |
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| 166 | Or -1 if the first is less than the second:
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| 167 |
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| 168 | = strcmp('a', 'aa') # => (Int) -1
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| 169 |
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| 170 | Or 1 if the first is greater than the second:
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| 171 |
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| 172 | = strcmp('z', 'a') # => (Int) 1
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| 173 |
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| 174 | ## List
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| 175 |
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| 176 | ### join()
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| 177 |
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| 178 | Given a List, stringify its items, and join them by a separator. The default
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| 179 | separator is the empty string.
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| 180 |
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| 181 | var x = ['a', 'b', 'c']
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| 182 |
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| 183 | echo $[join(x)] # => abc
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| 184 |
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| 185 | # optional separator
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| 186 | echo $[join(x, ' ')] # => a b c
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| 187 |
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| 188 | As a reminder, you can call it with the [fat-arrow][] operator `=>` for function chaining:
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| 189 |
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| 190 | var items = [1, 2, 3]
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| 191 |
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| 192 | json write (items => join()) # => "123"
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| 193 | json write (items => join(' ')) # => "1 2 3"
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| 194 | json write (items => join(', ')) # => "1, 2, 3"
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| 195 |
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| 196 | [fat-arrow]: chap-expr-lang.html#fat-arrow
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| 197 |
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| 198 | ## Dict
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| 199 |
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| 200 | ### keys()
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| 201 |
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| 202 | Returns all existing keys from a dict as a list of strings.
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| 203 |
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| 204 | var en2fr = {
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| 205 | hello: "bonjour",
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| 206 | friend: "ami",
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| 207 | cat: "chat"
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| 208 | }
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| 209 | = keys(en2fr)
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| 210 | # => (List 0x4689) ["hello","friend","cat"]
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| 211 |
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| 212 | ### values()
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| 213 |
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| 214 | Similar to `keys()`, but returns the values of the dictionary.
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| 215 |
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| 216 | var person = {
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| 217 | name: "Foo",
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| 218 | age: 25,
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| 219 | hobbies: :|walking reading|
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| 220 | }
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| 221 | = values(en2fr)
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| 222 | # => (List 0x4689) ["Foo",25,["walking","reading"]]
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| 223 |
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| 224 | ### get()
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| 225 |
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| 226 | Return value for given key, falling back to the default value if the key
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| 227 | doesn't exist.
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| 228 |
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| 229 | var book = {
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| 230 | title: "Hitchhiker's Guide",
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| 231 | published: 1979,
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| 232 | }
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| 233 |
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| 234 | var published = get(book, 'published', null)
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| 235 | = published
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| 236 | # => (Int) 1979
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| 237 |
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| 238 | var author = get(book, 'author', "???")
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| 239 | = author
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| 240 | # => (Str) "???"
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| 241 |
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| 242 | If not specified, the default value is `null`:
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| 243 |
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| 244 | var author = get(book, 'author')
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| 245 | = author
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| 246 | # => (Null) null
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| 247 |
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| 248 | ## Float
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| 249 |
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| 250 | ### floatsEqual()
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| 251 |
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| 252 | Check if two floating point numbers are equal.
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| 253 |
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| 254 | = floatsEqual(42.0, 42.0) # => (Bool) true
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| 255 |
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| 256 | It's usually better to make an approximate comparison:
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| 257 |
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| 258 | use $LIB_YSH/math.ysh --pick abs
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| 259 | var f1 = 0.3
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| 260 | var f2 = 0.4
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| 261 | = abs(f1 - f2) < 0.001 # => (Bool) false
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| 262 |
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| 263 | ## Obj
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| 264 |
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| 265 | Let's use this definition:
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| 266 |
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| 267 | var fields = {x: 42}
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| 268 | var obj = Obj.new(fields, null)
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| 269 |
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| 270 | ### first()
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| 271 |
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| 272 | Get the Dict that contains an object's properties.
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| 273 |
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| 274 | = first(obj) # => (Dict) {x: 42}
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| 275 |
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| 276 | The Dict and Obj share the same storage. So if the Dict is modified, the
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| 277 | object is too.
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| 278 |
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| 279 | If you want a copy, use `dict(obj)`.
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| 280 |
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| 281 | ### rest()
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| 282 |
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| 283 | Get the "prototype" of an Obj, which is another Obj, or null:
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| 284 |
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| 285 | = rest(obj) # => (Null) null
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| 286 |
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| 287 | ## Word
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| 288 |
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| 289 | ### maybe()
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| 290 |
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| 291 | Turn a string into a list, based on its emptiness.
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| 292 |
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| 293 | It's designed to be used to construct `argv` arrays, along with
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| 294 | [expr-splice][].
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| 295 |
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| 296 | var empty = ''
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| 297 | write -- ale @[maybe(empty)] corn # => ale corn
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| 298 |
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| 299 | var s = 'bean'
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| 300 | write -- ale @[maybe(s)] corn # => ale bean corn
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| 301 |
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| 302 | [expr-splice]: chap-word-lang.html#expr-splice
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| 303 |
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| 304 | ### shSplit()
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| 305 |
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| 306 | Split a string into a List of strings, using the shell algorithm that respects
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| 307 | `$IFS`.
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| 308 |
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| 309 | Prefer [split()][split] to `shSplit()`.
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| 310 |
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| 311 | [split]: chap-type-method.html#split
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| 312 |
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| 313 | ## Serialize
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| 314 |
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| 315 | ### toJson()
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| 316 |
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| 317 | Convert an object in memory to JSON text:
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| 318 |
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| 319 | = toJson({name: "alice"}) # => (Str) '{"name":"alice"}'
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| 320 |
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| 321 | Add indentation by passing the `space` param:
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| 322 |
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| 323 | = toJson([42], space=2) # => (Str) "[\n 42\n]"
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| 324 |
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| 325 | Turn non-serializable types into `null`, instead of raising an error:
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| 326 |
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| 327 | = toJson(/d+/, type_errors=false) # => (Str) 'null'
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| 328 |
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| 329 | The `toJson()` function is to `json write (x)`, except the default value of
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| 330 | `space` is 0.
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| 331 |
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| 332 | See [err-json-encode][] for errors.
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| 333 |
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| 334 | [err-json-encode]: chap-errors.html#err-json-encode
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| 335 |
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| 336 | ### fromJson()
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| 337 |
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| 338 | Convert JSON text to an object in memory:
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| 339 |
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| 340 | = fromJson('{"name":"alice"}') # => (Dict) {"name": "alice"}
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| 341 |
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| 342 | Similar to `json read <<< '{"name": "alice"}'`.
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| 343 |
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| 344 | See [err-json-decode][] for errors.
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| 345 |
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| 346 | [err-json-decode]: chap-errors.html#err-json-decode
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| 347 |
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| 348 | ### toJson8()
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| 349 |
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| 350 | Like `toJson()`, but it also converts binary data (non-Unicode strings) to
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| 351 | J8-style `b'foo \yff'` strings.
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| 352 |
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| 353 | In contrast, `toJson()` will do a lossy conversion with the Unicode replacement
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| 354 | character.
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| 355 |
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| 356 | See [err-json8-encode][] for errors.
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| 357 |
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| 358 | [err-json8-encode]: chap-errors.html#err-json8-encode
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| 359 |
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| 360 | ### fromJson8()
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| 361 |
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| 362 | Like `fromJson()`, but it also accepts binary data denoted by J8-style `b'foo
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| 363 | \yff'` strings.
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| 364 |
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| 365 | See [err-json8-decode][] for errors.
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| 366 |
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| 367 | [err-json8-decode]: chap-errors.html#err-json8-decode
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| 368 |
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| 369 | ## Pattern
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| 370 |
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| 371 | ### `_group()`
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| 372 |
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| 373 | Like `Match.group()`, but accesses the global match created by `~`:
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| 374 |
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| 375 | if ('foo42' ~ / d+ /) {
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| 376 | echo $[_group(0)] # => 42
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| 377 | }
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| 378 |
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| 379 | ### `_start()`
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| 380 |
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| 381 | Like `Match.start()`, but accesses the global match created by `~`:
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| 382 |
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| 383 | if ('foo42' ~ / d+ /) {
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| 384 | echo $[_start(0)] # => 3
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| 385 | }
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| 386 |
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| 387 | ### `_end()`
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| 388 |
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| 389 | Like `Match.end()`, but accesses the global match created by `~`:
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| 390 |
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| 391 | if ('foo42' ~ / d+ /) {
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| 392 | echo $[_end(0)] # => 5
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| 393 | }
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| 394 |
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| 395 | ## Reflection
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| 396 |
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| 397 | ### func/eval()
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| 398 |
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| 399 | This function is like [`io->eval()`][io/eval], but it disallows I/O.
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| 400 |
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| 401 | Example:
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| 402 |
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| 403 | var cmd = ^(const x = 42; )
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| 404 | = eval(cmd, to_dict=true) # => (Dict) {x: 42}
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| 405 |
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| 406 | [io/eval]: chap-type-method.html#io/eval
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| 407 |
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| 408 | ### func/evalExpr()
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| 409 |
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| 410 | This function is like [`io->evalExpr()`][io/evalExpr], but it disallows I/O.
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| 411 |
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| 412 | Example:
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| 413 |
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| 414 | var x = 42
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| 415 | var expr = ^[x + 1]
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| 416 | var val = evalExpr(expr) # 43
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| 417 |
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| 418 | [io/evalExpr]: chap-type-method.html#io/evalExpr
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| 419 |
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| 420 | ## Introspect
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| 421 |
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| 422 | ### `shvarGet()`
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| 423 |
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| 424 | Given a variable name, return its value. It uses the "dynamic scope" rule,
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| 425 | which looks up the stack for a variable.
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| 426 |
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| 427 | It's meant to be used with `shvar`:
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| 428 |
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| 429 | proc proc1 {
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| 430 | shvar PATH=/tmp { # temporarily set PATH in this stack frame
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| 431 | echo
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| 432 | }
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| 433 |
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| 434 | proc2
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| 435 | }
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| 436 |
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| 437 | proc proc2 {
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| 438 | proc3
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| 439 | }
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| 440 |
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| 441 | proc proc3 {
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| 442 | var path = shvarGet('PATH') # Look up the stack (dynamic scoping)
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| 443 | echo $path # => /tmp
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| 444 | }
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| 445 |
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| 446 | proc1
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| 447 |
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| 448 | Note that `shvar` is usually for string variables, and is analogous to `shopt`
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| 449 | for "booleans".
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| 450 |
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| 451 | If the variable isn't defined, `shvarGet()` returns `null`. So there's no way
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| 452 | to distinguish an undefined variable from one that's `null`.
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| 453 |
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| 454 | ### `getVar()`
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| 455 |
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| 456 | Given a variable name, return its value.
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| 457 |
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| 458 | var x = 42
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| 459 | = getVar('x') # => (Int) 42
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| 460 |
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| 461 | The variable may be local or global. (Compare with `shvarGet()`.) the "dynamic
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| 462 | scope" rule.)
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| 463 |
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| 464 | If the variable isn't defined, `getVar()` returns `null`. So there's no way to
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| 465 | distinguish an undefined variable from one that's `null`.
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| 466 |
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| 467 | ### `setVar()`
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| 468 |
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| 469 | Bind a name to a value, in the local scope. Returns nothing.
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| 470 |
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| 471 | call setVar('myname', 42)
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| 472 |
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| 473 | This is like
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| 474 |
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| 475 | setvar myname = 42
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| 476 |
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| 477 | except the name can is a string, which can be constructed at runtime.
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| 478 |
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| 479 | ---
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| 480 |
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| 481 | You can also bind globals:
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| 482 |
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| 483 | call setVar('myname', 42, global=true)
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| 484 |
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| 485 | which is like
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| 486 |
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| 487 | setglobal myname = 42
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| 488 |
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| 489 | ### `getShFunction`
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| 490 |
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| 491 | Given the name of a shell function, return the corresponding [Proc][] value, or
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| 492 | `null` if it's not found.
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| 493 |
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| 494 | [Proc]: chap-type-method.html#Proc
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| 495 |
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| 496 | ### `parseCommand()`
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| 497 |
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| 498 | Given a code string, parse it as a command (with the current parse options).
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| 499 |
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| 500 | Returns a `value.Command` instance, or raises an error.
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| 501 |
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| 502 | ### `parseExpr()`
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| 503 |
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| 504 | TODO:
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| 505 |
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| 506 | Given a code string, parse it as an expression.
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| 507 |
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| 508 | Returns a `value.Expr` instance, or raises an error.
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| 509 |
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| 510 | ### `bindFrame()`
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| 511 |
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| 512 | TODO
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| 513 |
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| 514 | ## Hay Config
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| 515 |
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| 516 | ### parseHay()
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| 517 |
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| 518 | ### evalHay()
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| 519 |
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| 520 |
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| 521 | ## Hashing
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| 522 |
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| 523 | ### sha1dc()
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| 524 |
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| 525 | Git's algorithm.
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| 526 |
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| 527 | ### sha256()
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| 528 |
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| 529 |
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| 530 | <!--
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| 531 |
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| 532 | ### Better Syntax
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| 533 |
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| 534 | These functions give better syntax to existing shell constructs.
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| 535 |
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| 536 | - `shQuote()` for `printf %q` and `${x@Q}`
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| 537 | - `trimLeft()` for `${x#prefix}` and `${x##prefix}`
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| 538 | - `trimRight()` for `${x%suffix}` and `${x%%suffix}`
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| 539 | - `trimLeftGlob()` and `trimRightGlob()` for slow, legacy glob
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| 540 | - `upper()` for `${x^^}`
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| 541 | - `lower()` for `${x,,}`
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| 542 | - `strftime()`: hidden in `printf`
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| 543 |
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| 544 | -->
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