[英]Linux script: Reinterpret environment variable
I am creating a Bash script which reads some other environment variables: 我正在创建一个Bash脚本,它读取一些其他环境变量:
echo "Exporting configuration variables..."
while IFS="=" read -r k v; do
key=$k
value=$v
if [[ ${#key} > 0 && ${#value} > 0 ]]; then
export $key=$value
fi
done < $HOME/myfile
and have the variable: 并有变量:
$a=$b/c/d/e
and want to call $a
as in: 并希望拨打$a
如下所示:
cp myOtherFile $a
The result for the destination folder for the copy is "$b/c/d/e", and an error is shown: 副本的目标文件夹的结果是“$ b / c / d / e”,并显示错误:
"$b/c/d/e" : No such file or directory
because it is interpreted literally as a folder path. 因为它实际上被解释为文件夹路径。
Can this path be reinterpreted before being used in the cp
command? 在cp
命令中使用之前,是否可以重新解释此路径?
It sounds like you want $HOME/myfile
to support Bash notations, such as parameter-expansion. 听起来你想要$HOME/myfile
来支持Bash符号,比如参数扩展。 I think the best way to do that is to modify $HOME/myfile
to be, in essence, a Bash script: 我认为最好的方法是修改$HOME/myfile
,实质上是一个Bash脚本:
export a=$b/c/d/e
and use the source
builtin to run it as part of the current Bash script: 并使用内置的source
将其作为当前Bash脚本的一部分运行:
source $HOME/myfile
... commands ...
cp myOtherFile "$a"
... commands ...
You need eval
to do this : 你需要eval
来做到这一点:
$ var=foo
$ x=var
$ eval $x=another_value
$ echo $var
another_value
I recommend you this doc before using eval
: http://mywiki.wooledge.org/BashFAQ/048 在使用eval
之前,我建议你使用这个文档: http : //mywiki.wooledge.org/BashFAQ/048
And a safer approach is to use declare
instead of eval
: 更安全的方法是使用declare
而不是eval
:
declare "$x=another_value"
Thanks to chepner 2 for the latest. 感谢最新的chepner 2。
尝试这个
cp myOtherFile `echo $a`
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