bash - iterate over lines in file and expand global variables -

i'm trying write bash script iterate on lines in file , expland global variables @ same time.

i have global variable $source_code_dir defined in bashrc file. lets $source_code_dir == /path/to/source/

my external file looks this:

$source_code_dir/some/dir/file.txt $source_code_dir/some/dir/file.cpp

and bash script far is:

while ifs=$'\n' read line   echo $line done < /path/to/external/file/above.txt

the variable $source_code_dir being used in other places in script, accessible , defined correctly;

the output of script

$source_code_dir/some/dir/file.txt $source_code_dir/some/dir/file.cpp

and not

/path/to/source/some/dir/file.txt /path/to/source/some/dir/file.cpp

can me expand $source_code_dir variable can use it?

one option use eval:

while ifs=$'\n' read line   eval echo $line done < /path/to/external/file/above.txt

Live