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 = 1337
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44 |
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45 | $ = type(d)
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46 | (Str) 'Dict'
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47 |
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48 | $ = type(n)
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49 | (Str) 'Int'
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50 |
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51 | Similar names: [type][]
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52 |
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53 | [type]: chap-index.html#type
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54 |
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55 | ### repeat()
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56 |
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57 | TODO:
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58 |
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59 | = repeat('a', 3)
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60 | (Str) 'aaa'
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61 |
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62 | = repeat(['a'], 3)
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63 | (List) ['a', 'a', 'a']
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64 |
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65 | Note that list elements are NOT copied. They are repeated by reference, which
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66 | means the List can have aliases.
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67 |
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68 | = repeat([[42]], 3)
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69 | (List) [[42], [42], [42]]
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70 |
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71 | Modeled after these Python expressions:
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72 |
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73 | >>> 'a' * 3
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74 | 'aaa'
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75 | >>> ['a'] * 3
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76 | ['a', 'a', 'a']
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77 |
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78 |
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79 | ## Conversions
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80 |
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81 | ### bool()
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82 |
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83 | Returns the truth value of its argument. Similar to `bool()` in python, it
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84 | returns `false` for:
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85 |
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86 | - `false`, `0`, `0.0`, `''`, `{}`, `[]`, and `null`.
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87 |
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88 | Returns `true` for all other values.
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89 |
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90 | ### int()
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91 |
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92 | Given a float, returns the largest integer that is less than its argument (i.e. `floor()`).
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93 |
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94 | $ = int(1.99)
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95 | (Int) 1
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96 |
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97 | Given a string, `Int()` will attempt to convert the string to a base-10
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98 | integer. The base can be overriden by calling with a second argument.
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99 |
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100 | $ = int('10')
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101 | (Int) 10
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102 |
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103 | $ = int('10', 2)
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104 | (Int) 2
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105 |
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106 | ysh$ = Int('foo')
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107 | # fails with an expression error
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108 |
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109 | ### float()
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110 |
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111 | Given an integer, returns the corressponding flaoting point representation.
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112 |
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113 | $ = float(1)
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114 | (Float) 1.0
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115 |
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116 | Given a string, `Float()` will attempt to convert the string to float.
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117 |
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118 | $ = float('1.23')
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119 | (Float) 1.23
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120 |
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121 | ysh$ = float('bar')
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122 | # fails with an expression error
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123 |
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124 | ### str()
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125 |
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126 | Converts a `Float` or `Int` to a string.
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127 |
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128 | ### list()
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129 |
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130 | Given a list, returns a shallow copy of the original.
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131 |
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132 | Given an iterable value (e.g. a range or dictionary), returns a list containing
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133 | one element for each item in the original collection.
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134 |
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135 | $ = list({'a': 1, 'b': 2})
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136 | (List) ['a', 'b']
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137 |
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138 | $ = list(1:5)
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139 | (List) [1, 2, 3, 4, 5]
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140 |
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141 | ### dict()
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142 |
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143 | Given a dictionary, returns a shallow copy of the original.
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144 |
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145 | ### runes()
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146 |
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147 | TODO
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148 |
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149 | Given a string, decodes UTF-8 into a List of integer "runes" (aka code points).
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150 |
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151 | Each rune is in the range `U+0` to `U+110000`, and **excludes** the surrogate
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152 | range.
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153 |
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154 | runes(s, start=-1, end=-1)
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155 |
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156 | TODO: How do we signal errors?
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157 |
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158 | (`runes()` can be used to implement implemented Python's `ord()`.)
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159 |
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160 | ### encodeRunes()
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161 |
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162 | TODO
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163 |
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164 | Given a List of integer "runes" (aka code points), return a string.
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165 |
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166 | (`encodeRunes()` can be used to implement implemented Python's `chr()`.)
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167 |
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168 | ### bytes()
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169 |
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170 | TODO
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171 |
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172 | Given a string, return a List of integer byte values.
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173 |
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174 | Each byte is in the range 0 to 255.
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175 |
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176 | ### encodeBytes()
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177 |
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178 | TODO
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179 |
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180 | Given a List of integer byte values, return a string.
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181 |
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182 | ## Str
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183 |
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184 | ### strcmp()
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185 |
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186 | TODO
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187 |
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188 | ### split()
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189 |
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190 | TODO
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191 |
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192 | If no argument is passed, splits by whitespace
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193 |
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194 | <!-- respecting Unicode space? -->
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195 |
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196 | If a delimiter Str with a single byte is given, splits by that byte.
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197 |
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198 | Modes:
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199 |
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200 | - Python-like algorithm
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201 | - Is awk any different?
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202 | - Split by eggex
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203 |
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204 | ### shSplit()
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205 |
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206 | Split a string into a List of strings, using the shell algorithm that respects
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207 | `$IFS`.
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208 |
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209 | Prefer `split()` to `shSplit()`.
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210 |
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211 |
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212 | ## List
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213 |
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214 | ### join()
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215 |
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216 | Given a List, stringify its items, and join them by a separator. The default
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217 | separator is the empty string.
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218 |
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219 | var x = ['a', 'b', 'c']
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220 |
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221 | $ echo $[join(x)]
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222 | abc
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223 |
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224 | $ echo $[join(x, ' ')] # optional separator
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225 | a b c
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226 |
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227 |
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228 | It's also often called with the `=>` chaining operator:
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229 |
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230 | var items = [1, 2, 3]
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231 |
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232 | json write (items => join()) # => "123"
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233 | json write (items => join(' ')) # => "1 2 3"
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234 | json write (items => join(', ')) # => "1, 2, 3"
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235 |
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236 | ## Float
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237 |
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238 | ### floatsEqual()
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239 |
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240 | Check if two floating point numbers are equal.
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241 |
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242 | = floatsEqual(42.0, 42.0)
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243 | (Bool) true
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244 |
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245 | It's usually better to make an approximate comparison:
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246 |
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247 | = abs(float1 - float2) < 0.001
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248 | (Bool) false
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249 |
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250 | ## Word
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251 |
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252 | ### glob()
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253 |
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254 | See `glob-pat` topic for syntax.
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255 |
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256 | ### maybe()
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257 |
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258 | ## Serialize
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259 |
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260 | ### toJson()
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261 |
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262 | Convert an object in memory to JSON text:
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263 |
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264 | $ = toJson({name: "alice"})
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265 | (Str) '{"name":"alice"}'
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266 |
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267 | Add indentation by passing the `space` param:
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268 |
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269 | $ = toJson([42], space=2)
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270 | (Str) "[\n 42\n]"
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271 |
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272 | Similar to `json write (x)`, except the default value of `space` is 0.
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273 |
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274 | See [err-json-encode][] for errors.
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275 |
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276 | [err-json-encode]: chap-errors.html#err-json-encode
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277 |
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278 | ### fromJson()
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279 |
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280 | Convert JSON text to an object in memory:
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281 |
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282 | = fromJson('{"name":"alice"}')
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283 | (Dict) {"name": "alice"}
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284 |
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285 | Similar to `json read <<< '{"name": "alice"}'`.
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286 |
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287 | See [err-json-decode][] for errors.
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288 |
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289 | [err-json-decode]: chap-errors.html#err-json-decode
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290 |
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291 | ### toJson8()
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292 |
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293 | Like `toJson()`, but it also converts binary data (non-Unicode strings) to
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294 | J8-style `b'foo \yff'` strings.
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295 |
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296 | In contrast, `toJson()` will do a lossy conversion with the Unicode replacement
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297 | character.
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298 |
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299 | See [err-json8-encode][] for errors.
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300 |
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301 | [err-json8-encode]: chap-errors.html#err-json8-encode
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302 |
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303 | ### fromJson8()
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304 |
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305 | Like `fromJson()`, but it also accepts binary data denoted by J8-style `b'foo
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306 | \yff'` strings.
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307 |
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308 | See [err-json8-decode][] for errors.
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309 |
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310 | [err-json8-decode]: chap-errors.html#err-json8-decode
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311 |
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312 | ## Pattern
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313 |
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314 | ### `_group()`
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315 |
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316 | Like `Match => group()`, but accesses the global match created by `~`:
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317 |
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318 | if ('foo42' ~ / d+ /) {
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319 | echo $[_group(0)] # => 42
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320 | }
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321 |
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322 | ### `_start()`
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323 |
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324 | Like `Match => start()`, but accesses the global match created by `~`:
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325 |
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326 | if ('foo42' ~ / d+ /) {
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327 | echo $[_start(0)] # => 3
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328 | }
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329 |
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330 | ### `_end()`
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331 |
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332 | Like `Match => end()`, but accesses the global match created by `~`:
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333 |
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334 | if ('foo42' ~ / d+ /) {
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335 | echo $[_end(0)] # => 5
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336 | }
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337 |
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338 | ## Introspection
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339 |
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340 | ### `shvarGet()`
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341 |
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342 | Given a variable name, return its value. It uses the "dynamic scope" rule,
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343 | which looks up the stack for a variable.
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344 |
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345 | It's meant to be used with `shvar`:
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346 |
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347 | proc proc1 {
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348 | shvar PATH=/tmp { # temporarily set PATH in this stack frame
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349 | my-proc
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350 | }
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351 |
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352 | proc2
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353 | }
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354 |
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355 | proc proc2 {
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356 | proc3
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357 | }
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358 |
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359 | proc proc3 {
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360 | var path = shvarGet('PATH') # Look up the stack (dynamic scoping)
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361 | echo $path # => /tmp
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362 | }
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363 |
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364 | proc1
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365 |
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366 | Note that `shvar` is usually for string variables, and is analogous to `shopt`
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367 | for "booleans".
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368 |
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369 | If the variable isn't defined, `shvarGet()` returns `null`. So there's no way
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370 | to distinguish an undefined variable from one that's `null`.
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371 |
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372 | ### `getVar()`
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373 |
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374 | Given a variable name, return its value.
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375 |
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376 | $ var x = 42
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377 | $ echo $[getVar('x')]
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378 | 42
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379 |
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380 | The variable may be local or global. (Compare with `shvarGet()`.) the "dynamic
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381 | scope" rule.)
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382 |
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383 | If the variable isn't defined, `getVar()` returns `null`. So there's no way to
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384 | distinguish an undefined variable from one that's `null`.
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385 |
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386 | ### `evalExpr()`
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387 |
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388 | Given a an expression quotation, evaluate it and return its value:
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389 |
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390 | $ var expr = ^[1 + 2]
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391 |
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392 | $ = evalExpr(expr)
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393 | 3
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394 |
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395 | ## Hay Config
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396 |
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397 | ### parseHay()
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398 |
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399 | ### evalHay()
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400 |
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401 |
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402 | ## Hashing
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403 |
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404 | ### sha1dc()
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405 |
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406 | Git's algorithm.
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407 |
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408 | ### sha256()
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409 |
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410 |
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411 | <!--
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412 |
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413 | ### Better Syntax
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414 |
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415 | These functions give better syntax to existing shell constructs.
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416 |
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417 | - `shQuote()` for `printf %q` and `${x@Q}`
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418 | - `trimLeft()` for `${x#prefix}` and `${x##prefix}`
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419 | - `trimRight()` for `${x%suffix}` and `${x%%suffix}`
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420 | - `trimLeftGlob()` and `trimRightGlob()` for slow, legacy glob
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421 | - `upper()` for `${x^^}`
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422 | - `lower()` for `${x,,}`
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423 | - `strftime()`: hidden in `printf`
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424 |
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425 | -->
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