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