1 | ---
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2 | title: Special Variables (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 **Special Variables**
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13 |
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14 | </div>
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15 |
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16 | This chapter describes special variables 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 | ## YSH Vars
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24 |
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25 | ### ARGV
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26 |
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27 | Replacement for `"$@"`
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28 |
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29 | ### ENV
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30 |
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31 | TODO
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32 |
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33 | ### _this_dir
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34 |
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35 | The directory the current script resides in. This knows about 3 situations:
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36 |
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37 | - The location of `oshrc` in an interactive shell
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38 | - The location of the main script, e.g. in `osh myscript.sh`
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39 | - The location of script loaded with the `source` builtin
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40 |
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41 | It's useful for "relative imports".
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42 |
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43 | ## YSH Status
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44 |
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45 | ### `_status`
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46 |
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47 | DEPRECATED: Use `_error.code` instead.
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48 |
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49 | ### `_error`
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50 |
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51 | A `Dict` that's set by the `try` builtin.
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52 |
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53 | The integer `_error.code` is always present:
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54 |
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55 | try {
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56 | ls /tmp
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57 | }
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58 | echo "status is $[_error.code]"
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59 |
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60 | Some errors also have a `message` field, like JSON/J8 encoding/decoding errors,
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61 | and user errors from the [error][] builtin.
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62 |
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63 | try {
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64 | echo $[toJson( /d+/ )] # invalid Eggex type
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65 | }
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66 | echo "failed: $[_error.message]" # => failed: Can't serialize ...
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67 |
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68 | [error]: chap-builtin-cmd.html#error
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69 |
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70 |
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71 | ### `_pipeline_status`
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72 |
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73 | After a pipeline of processes is executed, this array contains the exit code of
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74 | each process.
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75 |
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76 | Each exit code is an [Int](chap-type-method.html#Int). Compare with
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77 | [`PIPESTATUS`](#PIPESTATUS).
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78 |
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79 | ### `_process_sub_status`
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80 |
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81 | The exit status of all the process subs in the last command.
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82 |
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83 | ## YSH Tracing
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84 |
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85 | ### SHX_indent
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86 |
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87 | ### SHX_punct
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88 |
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89 | ### SHX_pid_str
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90 |
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91 | ## YSH Read
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92 |
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93 | ### _reply
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94 |
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95 | YSH `read` sets this variable:
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96 |
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97 | read --all < myfile
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98 | echo $_reply
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99 |
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100 | ## Oils VM
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101 |
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102 | ### `OILS_VERSION`
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103 |
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104 | The version of Oils that's being run, e.g. `0.23.0`.
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105 |
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106 | <!-- TODO: specify comparison algorithm. -->
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107 |
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108 | ### `LIB_OSH`
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109 |
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110 | The string `///osh`, which you can use with the [source][] builtin.
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111 |
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112 | source $LIB_OSH/two.sh
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113 |
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114 | [source]: chap-builtin-cmd.html#source
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115 |
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116 | ### `LIB_YSH`
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117 |
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118 | The string `///ysh`, which you can use with the [source][] builtin.
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119 |
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120 | source $LIB_YSH/yblocks.ysh
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121 |
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122 | [source]: chap-builtin-cmd.html#source
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123 |
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124 | ### `OILS_GC_THRESHOLD`
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125 |
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126 | At a GC point, if there are more than this number of live objects, collect
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127 | garbage.
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128 |
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129 | ### `OILS_GC_ON_EXIT`
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130 |
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131 | Set `OILS_GC_ON_EXIT=1` to explicitly collect and `free()` before the process
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132 | exits. By default, we let the OS clean up.
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133 |
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134 | Useful for ASAN testing.
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135 |
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136 | ### `OILS_GC_STATS`
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137 |
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138 | When the shell process exists, print GC stats to stderr.
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139 |
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140 | ### `OILS_GC_STATS_FD`
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141 |
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142 | When the shell process exists, print GC stats to this file descriptor.
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143 |
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144 | ## Float
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145 |
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146 | ### NAN
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147 |
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148 | The float value for "not a number".
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149 |
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150 | (The name is consistent with the C language.)
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151 |
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152 | ### INFINITY
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153 |
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154 | The float value for "infinity". You can negate it to get "negative infinity".
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155 |
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156 | (The name is consistent with the C language.)
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157 |
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158 | ## Shell Vars
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159 |
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160 | ### IFS
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161 |
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162 | Used for word splitting. And the builtin `shSplit()` function.
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163 |
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164 | ### LANG
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165 |
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166 | TODO: bash compat
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167 |
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168 | ### GLOBIGNORE
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169 |
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170 | TODO: bash compat
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171 |
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172 | ## Shell Options
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173 |
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174 | ### SHELLOPTS
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175 |
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176 | bash compat: serialized options for the `set` builtin.
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177 |
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178 | ### BASHOPTS
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179 |
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180 | bash compat: serialized options for the `shopt` builtin.
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181 |
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182 | ## Other Env
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183 |
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184 | ### HOME
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185 |
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186 | $HOME is used for:
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187 |
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188 | 1. ~ expansion
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189 | 2. ~ abbreviation in the UI (the dirs builtin, \W in $PS1).
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190 |
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191 | Note: The shell doesn't set $HOME. According to POSIX, the program that
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192 | invokes the login shell sets it based on /etc/passwd.
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193 |
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194 | ### PATH
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195 |
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196 | A colon-separated string that's used to find executables to run.
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197 |
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198 |
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199 | ## POSIX Special
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200 |
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201 | ## Other Special
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202 |
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203 | ### BASH_REMATCH
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204 |
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205 | Result of regex evaluation `[[ $x =~ $pat ]]`.
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206 |
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207 | ### PIPESTATUS
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208 |
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209 | After a pipeline of processes is executed, this array contains the exit code of
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210 | each process.
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211 |
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212 | Each exit code is a [Str](chap-type-method.html#Str). Compare with
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213 | [`_pipeline_status`](#_pipeline_status).
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214 |
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215 | ## Platform
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216 |
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217 | ### HOSTNAME
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218 |
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219 | The name of the "host" or machine that Oils is running on, determined by
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220 | `gethostname()`.
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221 |
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222 | ### OSTYPE
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223 |
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224 | The operating system that Oils is running on, determined by `uname()`.
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225 |
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226 | Examples: `linux darwin ...`
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227 |
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228 | ## Call Stack
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229 |
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230 | ### BASH_SOURCE
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231 |
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232 | ### FUNCNAME
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233 |
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234 | ### BASH_LINENO
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235 |
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236 | ## Tracing
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237 |
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238 | ### LINENO
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239 |
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240 | ## Process State
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241 |
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242 | ### BASHPID
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243 |
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244 | TODO
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245 |
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246 | ### PPID
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247 |
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248 | TODO
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249 |
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250 | ### UID
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251 |
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252 | ### EUID
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253 |
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254 | ## Process Stack
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255 |
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256 | ## Shell State
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257 |
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258 | ## Completion
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259 |
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260 | ### COMP_WORDS
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261 |
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262 | An array of words, split by : and = for compatibility with bash. New
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263 | completion scripts should use COMP_ARGV instead.
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264 |
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265 | ### COMP_CWORD
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266 |
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267 | Discouraged; for compatibility with bash.
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268 |
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269 | ### COMP_LINE
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270 |
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271 | Discouraged; for compatibility with bash.
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272 |
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273 | ### COMP_POINT
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274 |
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275 | Discouraged; for compatibility with bash.
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276 |
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277 | ### COMP_WORDBREAKS
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278 |
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279 | Discouraged; for compatibility with bash.
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280 |
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281 | ### COMPREPLY
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282 |
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283 | User-defined completion functions should Fill this array with candidates. It
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284 | is cleared on every completion request.
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285 |
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286 | ### COMP_ARGV
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287 |
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288 | An array of partial command arguments to complete. Preferred over COMP_WORDS.
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289 | The compadjust builtin uses this variable.
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290 |
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291 | (An OSH extension to bash.)
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292 |
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293 | ## History
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294 |
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295 | ### HISTFILE
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296 |
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297 | Override the default OSH history location.
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298 |
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299 | ### YSH_HISTFILE
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300 |
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301 | Override the default YSH history location.
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302 |
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303 | ## cd
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304 |
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305 | ### PWD
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306 |
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307 | ### OLDPWD
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308 |
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309 | ### CDPATH
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310 |
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311 | ## getopts
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312 |
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313 | ### OPTIND
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314 |
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315 | ### OPTARG
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316 |
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317 | ### OPTERR
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318 |
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319 | ## read
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320 |
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321 | ### REPLY
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322 |
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323 | OSH read sets this:
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324 |
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325 | read < myfile
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326 |
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327 | ## Functions
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328 |
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329 | ### RANDOM
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330 |
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331 | bash compat
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332 |
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333 | ### SECONDS
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334 |
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335 | bash compat
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336 |
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