Pattern: Parameter expansion starts with command substitution
Issue: -
ShellCheck found a parameter expansion that begins with a command substitution, such as $(..) or `..`. This is not valid. Parameter expansion only works on variables (normal or special).
In the example, the user hoped to apply the construct ${var##*/}, stripping the path, to the current git root directory as output by git rev-parse --show-toplevel. Since parameter expansion only works on variable, the command substitution must be assigned to a variable first like in the correct example.
Example of incorrect code:
echo "Building ${$(git rev-parse --show-toplevel)##*/}"Example of correct code:
tmp=$(git rev-parse --show-toplevel)
echo "Building ${tmp##*/}"