| 1 | ---
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| 2 | title: Builtin Commands (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) — Chapter **Standard Library**
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| 12 |
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| 13 | </div>
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| 14 |
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| 15 | This chapter in the [Oils Reference](index.html) describes the standard library
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| 16 | for OSH and YSH.
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| 17 |
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| 18 | (These functions are implemented in OSH or YSH, not C++ or Python.)
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| 19 |
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| 20 | <span class="in-progress">(in progress)</span>
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| 21 |
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| 22 | <div id="dense-toc">
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| 23 | </div>
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| 24 |
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| 25 | ## two
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| 26 |
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| 27 | These functions are in `two.sh`
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| 28 |
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| 29 | source $OSH_LIB/two.sh
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| 30 |
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| 31 | ### log
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| 32 |
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| 33 | Write a message to stderr:
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| 34 |
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| 35 | log "hi $x"
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| 36 | log '---'
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| 37 |
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| 38 | ### die
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| 39 |
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| 40 | Write an error message with the script name, and exit with status 1.
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| 41 |
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| 42 | die 'Expected a number'
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| 43 |
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| 44 | ## Args Parser
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| 45 |
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| 46 | YSH includes a command-line argument parsing utility called `parseArgs`. This
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| 47 | is intended to be used for command-line interfaces to YSH programs.
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| 48 |
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| 49 | To use it, first import `args.ysh`:
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| 50 |
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| 51 | source --builtin args.ysh
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| 52 |
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| 53 | Then, create an argument parser **spec**ification:
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| 54 |
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| 55 | parser (&spec) {
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| 56 | flag -v --verbose (help="Verbosely") # default is Bool, false
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| 57 |
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| 58 | flag -P --max-procs ('int', default=-1, help='''
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| 59 | Run at most P processes at a time
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| 60 | ''')
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| 61 |
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| 62 | flag -i --invert ('bool', default=true, help='''
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| 63 | Long multiline
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| 64 | Description
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| 65 | ''')
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| 66 |
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| 67 | arg src (help='Source')
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| 68 | arg dest (help='Dest')
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| 69 |
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| 70 | rest files
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| 71 | }
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| 72 |
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| 73 | Finally, parse `ARGV` (or any other array of strings) with:
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| 74 |
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| 75 | var args = parseArgs(spec, ARGV)
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| 76 |
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| 77 | The returned `args` is a `Dict` containing key-value pairs with the parsed
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| 78 | values (or defaults) for each flag and argument. For example, given
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| 79 | `ARGV = :| mysrc -P 12 mydest a b c |`, `args` would be:
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| 80 |
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| 81 | {
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| 82 | "verbose": false,
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| 83 | "max-procs": 12,
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| 84 | "invert": true,
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| 85 | "src": "mysrc",
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| 86 | "dest": "mydest",
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| 87 | "files": ["a", "b", "c"]
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| 88 | }
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| 89 |
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| 90 | ### parser
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| 91 |
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| 92 | `parseArgs()` requires a parser specification to indicate how to parse the
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| 93 | `ARGV` array. This specification should be constructed using the `parser` proc.
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| 94 |
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| 95 | parser (&spec) {
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| 96 | flag -f --my-flag
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| 97 | arg myarg
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| 98 | rest otherArgs
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| 99 | }
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| 100 |
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| 101 | In the above example, `parser` takes in a place `&spec`, which will store the
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| 102 | resulting specification and a block which is evaluated to build that
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| 103 | specification.
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| 104 |
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| 105 | Inside of a `parser` block, you should call the following procs:
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| 106 |
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| 107 | - `flag` to add `--flag` options
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| 108 | - `arg` to add positional arguments
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| 109 | - `rest` to capture remaining positional arguments into a list
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| 110 |
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| 111 | `parser` will validate the parser specification for errors such as duplicate
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| 112 | flag or argument names.
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| 113 |
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| 114 | parser (&spec) {
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| 115 | flag -n --name
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| 116 | flag -n --name # Duplicate!
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| 117 | }
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| 118 |
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| 119 | # => raises "Duplicate flag/arg name 'name' in spec" (status = 3)
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| 120 |
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| 121 | ### flag
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| 122 |
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| 123 | `flag` should be called within a `parser` block.
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| 124 |
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| 125 | parser (&spec) {
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| 126 | flag -v --verbose
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| 127 | }
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| 128 |
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| 129 | The above example declares a flag "--verbose" and a short alias "-v".
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| 130 | `parseArgs()` will then store a boolean value under `args.verbose`:
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| 131 | - `true` if the flag was passed at least once
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| 132 | - `false` otherwise
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| 133 |
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| 134 | Flags can also accept values. For example, if you wanted to accept an integer count:
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| 135 |
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| 136 | parser (&spec) {
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| 137 | flag -N --count ('int')
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| 138 | }
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| 139 |
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| 140 | Calling `parseArgs` with `ARGV = :| -n 5 |` or `ARGV = :| --count 5 |` will
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| 141 | store the integer `5` under `args.count`. If the user passes in a non-integer
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| 142 | value like `ARGV = :| --count abc |`, `parseArgs` will raise an error.
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| 143 |
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| 144 | Default values for an argument can be set with the `default` named argument.
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| 145 |
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| 146 | parser (&spec) {
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| 147 | flag -N --count ('int', default=2)
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| 148 |
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| 149 | # Boolean flags can be given default values too
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| 150 | flag -O --optimize ('bool', default=true)
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| 151 | }
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| 152 |
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| 153 | var args = parseArgs(spec, :| -n 3 |)
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| 154 | # => args.count = 2
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| 155 | # => args.optimize = true
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| 156 |
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| 157 | Each name passed to `flag` must be unique to that specific `parser`. Calling
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| 158 | `flag` with the same name twice will raise an error inside of `parser`.
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| 159 |
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| 160 | <!-- TODO: how can we explicitly pass false to a boolean flag? -->
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| 161 | <!-- TODO: how about --no-XXXX variants of flags? -->
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| 162 |
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| 163 | ### arg
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| 164 |
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| 165 | `arg` should be called within a `parser` block.
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| 166 |
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| 167 | parser (&spec) {
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| 168 | arg query
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| 169 | arg path
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| 170 | }
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| 171 |
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| 172 | The above example declares two positional arguments called "query" and "path".
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| 173 | `parseArgs()` will then store strings under `args.query` and `args.path`. Order
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| 174 | matters, so the first positional argument will be stored to `query` and the
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| 175 | second to `path`. If not enough positional arguments are passed, then
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| 176 | `parseArgs` will raise an error.
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| 177 |
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| 178 | Similar to `flag`, each `arg` name must be unique. Calling `arg` with the same
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| 179 | name twice will cause `parser` to raise an error.
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| 180 |
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| 181 | ### rest
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| 182 |
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| 183 | `rest` should be called within a `parser` block.
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| 184 |
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| 185 | parser (&spec) {
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| 186 | arg query
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| 187 | rest files
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| 188 | }
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| 189 |
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| 190 | Capture zero or more positional arguments not already captured by `arg`. So,
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| 191 | for `ARGV = :| hello file.txt message.txt README.md |`, we would have
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| 192 | `args.query = "file.txt"` and `args.files = ["file.txt", "message.txt",
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| 193 | "README.md"]`.
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| 194 |
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| 195 | Without rest, passing extraneous arguments will raise an error in
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| 196 | `parseArgs()`.
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| 197 |
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| 198 | `rest` can only be called _once_ within a `parser`. Calling it multiple times
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| 199 | will raise an error in `parser`.
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| 200 |
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| 201 | ### parseArgs()
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| 202 |
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| 203 | Given a parser specification `spec` produced by `parser`, parse a list of
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| 204 | strings (usually `ARGV`.)
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| 205 |
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| 206 | var args = parseArgs(spec, ARGV)
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| 207 |
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| 208 | The returned `args` is a dictionary mapping the names of each `arg`, `flag` and
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| 209 | `rest` to their captured values. (See the example at the [start of this
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| 210 | topic](#Args-Parser).)
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| 211 |
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| 212 | `parseArgs` will raise an error if the `ARGV` is invalid per the parser
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| 213 | specification. For example, if it's missing a required positional argument:
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| 214 |
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| 215 | parser (&spec) {
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| 216 | arg path
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| 217 | }
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| 218 |
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| 219 | var args = parseArgs(spec, [])
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| 220 | # => raises an error about the missing 'path' (status = 2)
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| 221 |
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| 222 | <!--
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| 223 | TODO: Document chaining parsers / sub-commands
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| 224 | - Either will allow parser nesting
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| 225 | - Or can use `rest rest` and `parseArgs` again on `rest`
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| 226 | TODO: Document the help named argument. Punting while we do not generate help messages
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| 227 | -->
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