Bash for循环if语句数组名称作为变量引用

Question

以下if [ {$i[0]} = "true" ]失败。我似乎无法弄清楚如何在if语句中获得{$i[0]}的正确格式。

#!/bin/bash
foo=bar1,bar2

for i in ${foo//,/" "}
do
declare -a ${i}='(true null null null)'
done

for i in ${foo//,/" "}
do
if [ {$i[0]} = "true" ]
then echo "yes"
eval "echo \${$i[*]}"
else echo "no"
fi
done

我有一个相关的问题，有人很友善地帮助我 Bash echo all array members when array is referenced as a variable in a loop

感谢您的帮助！

Answer 1

你也必须在这里使用eval，但我会再次推荐一个不同的整体设计。

if [ "$(eval "echo \${$i[0]}")" = "true" ]

修改

重新设计的提案（使用从我所看到的你所做的一点点推断出的假想场景）：

#!/bin/bash
# sample input: $1=foo,bar,baz
saveIFS=$IFS
IFS=','       # word splitting will be done using a comma as the delimiter
names=($1)    # store the names for cross reference or indirection
IFS=$saveIFS

# Constants:
declare -r heater=0
declare -r exhaust=1
declare -r light=2
declare -r rotation=3

# deserialize and serialize:

# initialize settings
for ((i=0; i<${#names}; i++))
do
    declare ${names[i]}=$i    # setup indirection pointers
    config[i]="null null null null"
done

# by index:
vals=(${config[0]})       # deserialize
echo ${vals[light]}       # output value
vals[light]="false"       # change it
config[0]=${vals[@]}      # reserialize

# by name:
vals=(${config[$foo]})
echo ${vals[light]}       # output value

# by indirection:
vals=(${config[${!names[0]}]})
echo ${vals[light]}       # output value

# iteration using indirection
for name in ${names[@]}
do
    echo "Configuration: $name"
    echo "  all settings: ${config[${!name}]}"
    vals=(${config[${!name}]})
    for setting in heater light # skipping exhaust and rotation
    do
        echo "    $setting: ${vals[${!setting}]}"
    done
done

这可能会为您提供一些您可以使用的想法和原则。如果你正在使用Bash 4，你可以使用关联数组，这将大大简化这种类型的事情。您还可以使用函数进行一些简化。