| 1 | ---
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| 2 | title: Plugins and Hooks (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 **Plugins and Hooks**
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| 13 |
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| 14 | </div>
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| 15 |
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| 16 | This chapter describes extension points for OSH and YSH.
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| 17 |
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| 18 | <span class="in-progress">(in progress)</span>
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| 19 |
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| 20 | <div id="dense-toc">
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| 21 | </div>
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| 22 |
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| 23 | ## Signals
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| 24 |
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| 25 | ### SIGTERM
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| 26 |
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| 27 | SIGTERM is the default signal sent by `kill`. It asks a process to terminate.
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| 28 |
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| 29 | You can register a SIGTERM handler with the [trap][] builtin.
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| 30 |
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| 31 | [trap]: chap-builtin-cmd.html#trap
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| 32 |
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| 33 | ### SIGINT
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| 34 |
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| 35 | SIGINT is usually generated by Ctrl-C. It interrupts what the shell is doing
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| 36 | and returns to the prompt.
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| 37 |
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| 38 | You can register a SIGINT handler with the [trap][] builtin.
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| 39 |
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| 40 | ### SIGQUIT
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| 41 |
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| 42 | SIGQUIT is usually generated by Ctrl-\.
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| 43 |
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| 44 | ### SIGTTIN
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| 45 |
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| 46 | Used by the job control implementation.
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| 47 |
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| 48 | ### SIGTTOU
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| 49 |
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| 50 | Used by the job control implementation.
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| 51 |
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| 52 | ### SIGWINCH
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| 53 |
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| 54 | Oils receives this signal when the terminal window size changes.
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| 55 |
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| 56 | ## Traps
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| 57 |
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| 58 | ### DEBUG
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| 59 |
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| 60 | Runs code before "leaf" commands, like
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| 61 |
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| 62 | echo hi
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| 63 | a=b
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| 64 | [[ x -eq y ]]
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| 65 | (( a = 42 ))
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| 66 |
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| 67 | But not before `{`:
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| 68 |
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| 69 | { echo one; echo two; }
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| 70 |
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| 71 | ---
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| 72 |
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| 73 | See the [Quirks doc](../quirks.html) for an interaction between the `DEBUG`
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| 74 | trap, pipelines, and interactive shells.
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| 75 |
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| 76 | ### ERR
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| 77 |
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| 78 | TODO
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| 79 |
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| 80 | ### EXIT
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| 81 |
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| 82 | TODO
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| 83 |
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| 84 | ### RETURN
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| 85 |
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| 86 | TODO
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| 87 |
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| 88 | ## Words
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| 89 |
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| 90 | <!--
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| 91 | <h3 id="PS1">PS1</h3>
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| 92 | -->
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| 93 |
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| 94 | ### PS1
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| 95 |
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| 96 | First line of the shell prompt.
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| 97 |
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| 98 | ### PS2
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| 99 |
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| 100 | Second line of the shell prompt (unimplemented).
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| 101 |
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| 102 | ### PS3
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| 103 |
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| 104 | For the `select` builtin (unimplemented).
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| 105 |
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| 106 | ### PS4
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| 107 |
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| 108 | The prefix of each line of output in `set -x` aka `set -o xtrace`. The leading
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| 109 | character is special.
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| 110 |
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| 111 | ## Completion
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| 112 |
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| 113 | ### complete
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| 114 |
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| 115 | The [complete][] builtin calls back into the shell evaluator to create
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| 116 | candidate strings for autocompletion:
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| 117 |
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| 118 | - `-C` is an external command that's executed
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| 119 | - `-F` is the name of a shell function name that's run
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| 120 | - `-W` is a word list that's evalutaed
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| 121 |
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| 122 | [complete]: chap-builtin-cmd.html#complete
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| 123 |
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| 124 | ## Other Plugin
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| 125 |
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| 126 | ### PROMPT_COMMAND
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| 127 |
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| 128 | A command that's executed before each prompt.
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| 129 |
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| 130 | This feature is taken from [bash]($xref).
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| 131 |
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| 132 | ## YSH
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| 133 |
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| 134 | ### renderPrompt()
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| 135 |
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| 136 | Users may define this func to customize their prompt.
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| 137 |
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| 138 | The func should take the global `value.IO` instance, and return a prompt string
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| 139 | (type `value.Str`).
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| 140 |
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| 141 | To construct the prompt, it can make calls like
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| 142 | [`io->promptVal('$')`]($chap-type-method:promptVal).
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| 143 |
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| 144 | To render the prompt, YSH first checks if this function exists. Otherwise, it
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| 145 | uses [`$PS1`]($chap-plugin:PS1) with a `ysh` prefix.
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| 146 |
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| 147 | <!-- note: doctools/cmark.py turns promptVal -> promptval -->
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| 148 |
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| 149 |
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