Parse ${} placeholder into absolute path in shell script - bash

Question

I have a app.properties file something like below
Base.dir="/user/test/application"
Result.dir="${base.dir}/result"
and i've create bash script to parse above properties
function readConfigFile()
{
(grep -E "^${2}=" -m 1 "${1}" 2>/dev/null || echo "VAR=__UNDEFINED__") | head -n 1 | cut -d '=' -f 2-;
}
function setConfigFile()
{
sourceFile=${1}
}
function configGet()
{
if [ ! -z $sourceFile ]; then
val="$(readConfigFile $sourceFile "${1}")";
if [ "${val}" = "__UNDEFINED__" ]; then
echo "${1} value not exist"
# return empty string
printf -- "%s" "";
fi
printf -- "%s" "${val}";
else
echo "config file not exist"
# return empty string
printf -- "%s" "";
fi
}
and the way i call above parser is something like below
$Result_dir=$(configGet Result.dir)
however, i cant really translate placeholder ${} into base_dir
and i got following error
ls $Result_dir
ls: cannot access ${Base_dir}/result: No such file or directory
Is there any way that i can translate ${Base.dir} into /user/test/application?

Answer 1

I guess you're not going to be able to substitute ${base.dir} (btw shouldn't it be ${Base.dir}?) the way you were hoping mainly because, as far as I know, dots are not allowed in variable names in bash.
What you could do is manually substitute the ${base.dir} part with the corresponding path using bash's substitution syntax. For example:
setConfigFile 'app.properties'
Result_dir_raw=$(configGet Result.dir)
Result_dir=${Result_dir_raw/'${base.dir}'/$(configGet Base.dir)}
echo ${Result_dir}
I say "manually" because you still specify in your source code that the pattern you want to replace is ${base.dir} which I'm guessing isn't what you wanted.
Now if you run this you'll see that the ${Result_dir} variable evaluates to ""/user/test/application"/result" which obviously isn't a path, and this is because you're surrounding the paths in app.properties with double quotes, so you either need to get rid of them in your readConfigFile function or lose them altogether in your config file, which to me makes more sense.

Answer 2

Why have you a . in your variable name, which is not allowed in bash:
$ Base.dir="/user/test/application"
-bash: Base.dir=/user/test/application: No such file or directory
$ Base_dir="/user/test/application"
$
So, why do you get No such file or directory? Here is an explanation:
Create a file called Base.dir=gash.sh, yes, that's a legal filename
$ echo 'echo Hello World' > Base.dir=gash.sh
Make the file executable:
$ PATH=$PATH:.
$ chmod u+x Base.dir=gash.sh
Now type the command:
$ Base.dir="gash.sh"
Hello World
Use an underscore, not a dot. By the Way, ksh Korn shell not only allows the dot, it has a special meaning, it is a compound variable.