如何在unix中获取变量（参数扩展）的变量值？

Question

How to fetch value of variable of variable (parameter expansion) in unix?

I have a text file(comma separated) filename='workdir.txt' as below which I am reading in unix shell script:

$AC_WORKDIR,current,FILE

$AC_WORKDIR,1 week,DIR

and so on

$AC_WORKDIR is env varriable AC_WORKDIR="/home/ascxd01/data/workdir" already defined.

My code is as below:

filename='workdir.txt'

while read line; do

work_dir=`echo $line | cut -d',' -f1`

echo "$work_dir"

done< $filename

When I am doing echo "$work_dir" its giving me $AC_WORKDIR however I want the actual value of $AC_WORKDIR which is "/home/ascxd01/data/workdir"

Please tell me how to do it.

Answer 1

If you drop the leading $ the indirect expansion should work normally, eg.

while read line; do
    work_dir=`echo $line | cut -d',' -f1 | tr -d '$'` # delete "$"
    echo "${!work_dir}"
done< $filename

The linked answer provides other maybe less good alternatives that would work, like eval "echo $work_dir" .