1 | ## compare_shells: bash
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2 |
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3 | #### var ref to array 'preHooks[@]'
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4 | #
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5 | # This idiom discussed on
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6 | # https://github.com/NixOS/nixpkgs/pull/147629
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7 |
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8 | show() {
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9 | echo show
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10 |
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11 | # These are actually different
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12 | argv.py ${!hooksSlice}
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13 |
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14 | argv.py ${!hooksSlice+"${!hooksSlice}"}
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15 | }
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16 |
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17 | hooksSlice='preHooks[@]'
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18 |
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19 | preHooks=()
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20 | show
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21 |
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22 | preHooks=('foo bar' baz)
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23 | show
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24 |
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25 | # WTF this exposes a difference? But not the test case below?
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26 |
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27 | # What's happening here?
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28 | # Uncomment this and get an error in bash about hookSlice, even though we never
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29 | # undefined it.
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30 |
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31 | #wtf=1
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32 | #
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33 | # line 6: !hooksSlice: unbound variable
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34 |
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35 | if test -n "$wtf"; then
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36 | # 4.4.0(1)-release
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37 | # echo $BASH_VERSION
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38 |
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39 | set -u
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40 | preHooks=()
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41 | show
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42 |
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43 | preHooks=('foo bar' baz)
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44 | show
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45 | fi
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46 |
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47 | ## STDOUT:
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48 | show
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49 | []
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50 | []
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51 | show
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52 | ['foo', 'bar', 'baz']
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53 | ['foo bar', 'baz']
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54 | ## END
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55 |
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56 | #### Similar to above with set -u
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57 | show() {
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58 | echo show
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59 |
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60 | # bash gives an error here - !hookSlice unbound, even though preHooks exists
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61 | # OSH currently does the "logical" thing
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62 |
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63 | # NOT testing this -- I think this is WHAT NIX WORKS AROUND WITH
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64 | #argv.py ${!hooksSlice}
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65 |
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66 | argv.py ${!hooksSlice+"${!hooksSlice}"}
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67 | }
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68 |
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69 | hooksSlice='preHooks[@]'
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70 |
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71 | set -u
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72 | preHooks=()
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73 | show
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74 |
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75 | preHooks=('foo bar' baz)
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76 | show
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77 |
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78 | ## STDOUT:
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79 | show
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80 | []
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81 | show
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82 | ['foo bar', 'baz']
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83 | ## END
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84 |
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85 | #### ${!ref} to undefined array
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86 |
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87 | set -u
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88 | shopt -s eval_unsafe_arith || true 2>/dev/null
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89 |
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90 | #preHooks=()
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91 | hookSlice="preHooks[@]"
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92 |
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93 | argv.py ${!hookSlice+"${!hookSlice}"}
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94 |
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95 | for element in ${!hookSlice+"${!hookSlice}"}; do
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96 | echo $element
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97 | done
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98 |
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99 | ## STDOUT:
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100 | []
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101 | ## END
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102 |
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103 | #### ${!ref} to undefined string var is fatal, INCONSISTENT with array
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104 | hookSlice='preHooks'
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105 |
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106 | argv.py ${!hookSlice}
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107 |
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108 | set -u
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109 |
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110 | argv.py ${!hookSlice}
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111 |
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112 | echo end
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113 |
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114 | ## status: 1
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115 | ## STDOUT:
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116 | []
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117 | ## END
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118 |
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119 | #### export with dynamic var name +=
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120 |
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121 | orig() {
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122 | export NIX_LDFLAGS${role_post}+=" -L$1/lib64"
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123 | }
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124 |
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125 | new() {
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126 | local var_name="NIX_LDFLAGS$role_post"
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127 | local value=" -L$1/lib64"
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128 |
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129 | eval "$var_name"+='$value'
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130 | export "$var_name"
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131 | }
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132 |
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133 | role_post='_foo'
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134 |
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135 | # set -u
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136 |
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137 | if test -n "${BASH_VERSION:-}"; then
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138 | orig one
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139 | fi
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140 |
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141 | declare -p NIX_LDFLAGS_foo # inspect it
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142 | unset NIX_LDFLAGS_foo
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143 |
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144 | new one
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145 |
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146 | declare -p NIX_LDFLAGS_foo # inspect it
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147 |
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148 | ## STDOUT:
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149 | declare -x NIX_LDFLAGS_foo=" -Lone/lib64"
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150 | declare -x NIX_LDFLAGS_foo=" -Lone/lib64"
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151 | ## END
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152 | ## OK osh STDOUT:
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153 | declare -x NIX_LDFLAGS_foo=' -Lone/lib64'
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154 | ## END
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155 |
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156 | #### let idiom can be written in POSIX shell - eval ": \$(( ))"
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157 |
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158 | for i in 0 1 2; do
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159 | echo i=$i
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160 |
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161 | NIX_ENFORCE_NO_NATIVE=$i
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162 |
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163 | outputVar=NIX_ENFORCE_NO_NATIVE_x86_64_unknown_linux_gnu
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164 | inputVar=NIX_ENFORCE_NO_NATIVE
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165 |
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166 | # Original Nix idiom
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167 |
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168 | if test -n "$BASH_VERSION"; then
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169 | let "${outputVar} |= ${!inputVar:-0}" "1"
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170 | else
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171 | # OSH alternative
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172 | eval ": \$(( ${outputVar} |= ${!inputVar:-0} ))"
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173 | fi
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174 |
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175 | echo NIX_ENFORCE_NO_NATIVE=$NIX_ENFORCE_NO_NATIVE
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176 | echo NIX_ENFORCE_NO_NATIVE_x86_64_unknown_linux_gnu=$NIX_ENFORCE_NO_NATIVE_x86_64_unknown_linux_gnu
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177 | echo
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178 |
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179 | done
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180 |
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181 |
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182 | ## STDOUT:
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183 | i=0
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184 | NIX_ENFORCE_NO_NATIVE=0
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185 | NIX_ENFORCE_NO_NATIVE_x86_64_unknown_linux_gnu=0
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186 |
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187 | i=1
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188 | NIX_ENFORCE_NO_NATIVE=1
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189 | NIX_ENFORCE_NO_NATIVE_x86_64_unknown_linux_gnu=1
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190 |
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191 | i=2
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192 | NIX_ENFORCE_NO_NATIVE=2
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193 | NIX_ENFORCE_NO_NATIVE_x86_64_unknown_linux_gnu=3
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194 |
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195 | ## END
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196 |
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