1 | ## compare_shells: bash-4.4 mksh zsh
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2 |
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3 | #### (( )) result
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4 | (( 1 )) && echo True
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5 | (( 0 )) || echo False
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6 | ## STDOUT:
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7 | True
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8 | False
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9 | ## END
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10 |
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11 | #### negative number is true
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12 | (( -1 )) && echo True
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13 | ## stdout: True
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14 |
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15 | #### (( )) in if statement
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16 | if (( 3 > 2)); then
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17 | echo True
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18 | fi
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19 | ## stdout: True
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20 |
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21 | #### (( ))
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22 | # What is the difference with this and let? One difference: spaces are allowed.
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23 | (( x = 1 ))
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24 | (( y = x + 2 ))
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25 | echo $x $y
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26 | ## stdout: 1 3
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27 |
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28 | #### (( )) with arrays
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29 | a=(4 5 6)
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30 | (( sum = a[0] + a[1] + a[2] ))
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31 | echo $sum
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32 | ## stdout: 15
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33 | ## OK zsh stdout: 9
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34 |
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35 | #### (( )) with error
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36 | (( a = 0 )) || echo false
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37 | (( b = 1 )) && echo true
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38 | (( c = -1 )) && echo true
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39 | echo $((a + b + c))
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40 | ## STDOUT:
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41 | false
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42 | true
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43 | true
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44 | 0
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45 | ## END
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46 |
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47 |
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48 | #### bash and mksh: V in (( a[K] = V )) gets coerced to integer
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49 | shopt -u strict_arith || true
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50 | K=key
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51 | V=value
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52 | typeset -a a
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53 | (( a[K] = V ))
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54 |
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55 | # not there!
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56 | echo a[\"key\"]=${a[$K]}
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57 |
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58 | echo keys = ${!a[@]}
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59 | echo values = ${a[@]}
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60 | ## STDOUT:
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61 | a["key"]=0
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62 | keys = 0
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63 | values = 0
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64 | ## END
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65 | ## N-I zsh status: 1
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66 | ## N-I zsh stdout-json: ""
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67 |
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68 | #### bash: K in (( A[K] = V )) is a constant string
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69 | K=5
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70 | V=42
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71 | typeset -A A
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72 | (( A[K] = V ))
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73 |
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74 | echo A["5"]=${A["5"]}
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75 | echo keys = ${!A[@]}
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76 | echo values = ${A[@]}
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77 | ## STDOUT:
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78 | A[5]=
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79 | keys = K
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80 | values = 42
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81 | ## END
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82 | ## OK osh status: 1
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83 | ## OK osh stdout-json: ""
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84 | ## N-I zsh status: 1
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85 | ## N-I zsh stdout-json: ""
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86 | ## N-I mksh status: 1
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87 | ## N-I mksh stdout-json: ""
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88 |
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89 | #### BUG: (( V = A[K] )) doesn't retrieve the right value
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90 | typeset -A A
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91 | K=5
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92 | V=42
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93 | A["$K"]=$V
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94 | A["K"]=oops
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95 | A[K]=oops2
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96 |
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97 | # We don't neither 42 nor "oops". Bad!
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98 | (( V = A[K] ))
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99 |
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100 | echo V=$V
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101 | ## status: 1
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102 | ## stdout-json: ""
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103 | ## BUG bash/zsh status: 0
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104 | ## BUG bash/zsh STDOUT:
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105 | V=0
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106 | ## END
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107 |
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108 | #### bash: V in (( A["K"] = V )) gets coerced to integer
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109 | shopt -u strict_arith || true
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110 | K=key
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111 | V=value
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112 | typeset -A A || exit 1
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113 | (( A["K"] = V ))
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114 |
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115 | # not there!
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116 | echo A[\"key\"]=${A[$K]}
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117 |
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118 | echo keys = ${!A[@]}
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119 | echo values = ${A[@]}
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120 | ## STDOUT:
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121 | A["key"]=
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122 | keys = K
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123 | values = 0
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124 | ## END
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125 | ## N-I zsh stdout-json: ""
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126 | ## N-I zsh status: 1
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127 | ## N-I mksh stdout-json: ""
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128 | ## N-I mksh status: 1
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129 |
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130 | #### literal strings inside (( ))
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131 | declare -A A
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132 | A['x']=42
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133 | (( x = A['x'] ))
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134 | (( A['y'] = 'y' )) # y is a variable, gets coerced to 0
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135 | echo $x ${A['y']}
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136 | ## STDOUT:
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137 | 42 0
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138 | ## END
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139 | ## N-I mksh status: 0
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140 | ## N-I mksh STDOUT:
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141 | 0
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142 | ## END
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143 | ## N-I zsh status: 0
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144 | ## N-I zsh STDOUT:
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145 | 42
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146 | ## END
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147 |
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148 | #### (( )) with redirect
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149 | (( a = $(stdout_stderr.py 42) + 10 )) 2>$TMP/x.txt
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150 | echo $a
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151 | echo --
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152 | cat $TMP/x.txt
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153 | ## STDOUT:
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154 | 52
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155 | --
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156 | STDERR
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157 | ## END
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158 |
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159 | #### Assigning whole raray (( b = a ))
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160 | a=(4 5 6)
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161 | (( b = a ))
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162 |
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163 | echo "${a[@]}"
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164 |
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165 | # OSH doesn't like this
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166 | echo "${b[@]}"
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167 |
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168 | ## status: 0
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169 | ## STDOUT:
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170 | 4 5 6
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171 | 4
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172 | ## END
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173 | ## BUG zsh status: 0
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174 | ## BUG zsh STDOUT:
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175 | 4 5 6
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176 |
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177 | ## END
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178 |
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179 | #### set associative array
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180 | declare -A A=(['foo']=bar ['spam']=42)
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181 | (( x = A['spam'] ))
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182 | echo $x
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183 | ## STDOUT:
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184 | 42
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185 | ## END
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186 | ## N-I mksh status: 1
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187 | ## N-I mksh stdout-json: ""
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188 | ## N-I zsh STDOUT:
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189 | 0
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190 | ## END
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191 |
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192 | #### Example of incrementing associative array entry with var key (ble.sh)
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193 | declare -A A=(['foo']=42)
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194 | key='foo'
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195 |
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196 | # note: in bash, (( A[\$key] += 1 )) works the same way.
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197 |
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198 | set -- 1 2
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199 | (( A[$key] += $2 ))
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200 |
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201 | echo foo=${A['foo']}
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202 |
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203 | ## STDOUT:
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204 | foo=44
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205 | ## END
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206 | ## N-I mksh/zsh status: 1
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207 | ## N-I mksh/zsh stdout-json: ""
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208 |
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