| 1 | ---
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| 2 | title: Word Language (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 **Word Language**
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| 13 |
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| 14 | </div>
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| 15 |
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| 16 | This chapter describes the word language for OSH and YSH. Words evaluate to
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| 17 | strings, or arrays of strings.
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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 | <h2 id="expression">Expressions to Words</h2>
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| 25 |
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| 26 | ### expr-sub
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| 27 |
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| 28 | ### expr-splice
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| 29 |
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| 30 | ### var-splice
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| 31 |
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| 32 | <h2 id="formatting">Formatting Typed Data as Strings</h2>
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| 33 |
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| 34 | ### ysh-printf
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| 35 |
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| 36 | ### ysh-format
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| 37 |
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| 38 |
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| 39 | ## Quotes
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| 40 |
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| 41 | ### osh-string
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| 42 |
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| 43 | - Single quotes
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| 44 | - Double Quotes
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| 45 | - C-style strings: `$'\n'`
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| 46 |
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| 47 | TODO: elaborate
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| 48 |
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| 49 | ### ysh-string
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| 50 |
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| 51 | YSH strings in the word language are the same as in the expression language.
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| 52 |
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| 53 | See [ysh-string in chap-expr-lang](chap-expr-lang.html#ysh-string).
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| 54 |
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| 55 | ### triple-quoted
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| 56 |
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| 57 | Triple-quoted in the word language are the same as in the expression language.
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| 58 |
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| 59 | See [triple-quoted in chap-expr-lang](chap-expr-lang.html#triple-quoted).
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| 60 |
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| 61 | ### tagged-str
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| 62 |
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| 63 | Not done.
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| 64 |
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| 65 | ## Substitutions
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| 66 |
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| 67 | ### command-sub
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| 68 |
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| 69 | Executes a command and captures its stdout.
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| 70 |
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| 71 | OSH has shell-compatible command sub like `$(echo hi)`. If a trailing newline
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| 72 | is returned, it's removed:
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| 73 |
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| 74 | $ hostname
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| 75 | example.com
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| 76 |
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| 77 | $ echo "/tmp/$(hostname)"
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| 78 | /tmp/example.com
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| 79 |
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| 80 | YSH has spliced command subs, enabled by `shopt --set parse_at`. The reuslt is
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| 81 | a **List** of strings, rather than a single string.
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| 82 |
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| 83 | $ write -- @(echo foo; echo 'with spaces')
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| 84 | foo
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| 85 | with-spaces
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| 86 |
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| 87 | The command's stdout parsed as the "J8 Lines" format, where each line is
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| 88 | either:
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| 89 |
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| 90 | 1. An unquoted string, which must be valid UTF-8. Whitespace is allowed, but
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| 91 | not other ASCII control chars.
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| 92 | 2. A quoted J8 string (JSON style `""` or J8-style `b'' u'' ''`)
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| 93 | 3. An **ignored** empty line
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| 94 |
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| 95 | See [J8 Notation](../j8-notation.html) for more details.
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| 96 |
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| 97 | ### var-sub
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| 98 |
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| 99 | Evaluates to the value of a variable:
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| 100 |
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| 101 | $ x=X
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| 102 | $ echo $x ${x}
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| 103 | X X
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| 104 |
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| 105 | ### arith-sub
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| 106 |
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| 107 | Shell has C-style arithmetic:
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| 108 |
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| 109 | $ echo $(( 1 + 2*3 ))
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| 110 | 7
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| 111 |
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| 112 | ### tilde-sub
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| 113 |
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| 114 | Used as a shortcut for a user's home directory:
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| 115 |
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| 116 | ~/src # my home dir
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| 117 | ~bob/src # user bob's home dir
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| 118 |
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| 119 | ### proc-sub
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| 120 |
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| 121 | Open stdout as a named file in `/dev/fd`, which can be passed to a command:
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| 122 |
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| 123 | diff <(sort L.txt) <(sort R.txt)
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| 124 |
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| 125 | Open stdin as a named file in `/dev/fd`:
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| 126 |
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| 127 | seq 3 | tee >(sleep 1; tac)
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| 128 |
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| 129 |
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| 130 | ## Var Ops
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| 131 |
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| 132 | ### op-test
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| 133 |
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| 134 | ### op-strip
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| 135 |
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| 136 | ### op-replace
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| 137 |
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| 138 | ### op-index
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| 139 |
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| 140 | ${a[i+1]}
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| 141 |
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| 142 | ### op-slice
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| 143 |
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| 144 | ### op-format
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| 145 |
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| 146 | ${x@P} evaluates x as a prompt string, e.g. the string that would be printed if
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| 147 | PS1=$x.
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| 148 |
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