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 a 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 a prompt.
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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 | For 'set -o xtrace'. The leading character is special.
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109 |
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110 | ## Completion
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111 |
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112 | ### complete
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113 |
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114 | The [complete][] builtin calls back into the shell evaluator to create
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115 | candidate strings for autocompletion:
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116 |
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117 | - `-C` is an external command that's executed
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118 | - `-F` is the name of a shell function name that's run
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119 | - `-W` is a word list that's evalutaed
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120 |
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121 | [complete]: chap-builtin-cmd.html#complete
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122 |
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123 | ## Other Plugin
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124 |
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125 | ### PROMPT_COMMAND
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126 |
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127 | A command that's executed before each prompt.
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128 |
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129 | This feature is taken from [bash]($xref).
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130 |
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131 | ## YSH
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132 |
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133 | ### renderPrompt()
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134 |
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135 | Users may define this func to customize their prompt.
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136 |
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137 | The func should take the global `value.IO` instance, and return a prompt string
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138 | (type `value.Str`).
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139 |
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140 | To construct the prompt, it can make calls like
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141 | [`io->promptVal('$')`]($chap-type-method:promptVal).
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142 |
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143 | To render the prompt, YSH first checks if this function exists. Otherwise, it
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144 | uses [`$PS1`]($chap-plugin:PS1) with a `ysh` prefix.
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145 |
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146 | <!-- note: doctools/cmark.py turns promptVal -> promptval -->
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147 |
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148 |
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