TronBox comes with a built-in flatten task that lets you combine the source code of multiple Solidity files.
Note:This function requires TronBox V3.3.0 or later.
Flattening specific files
If you want to flatten the specific file, you can use the flatten task. The flatten task can receive a path to the file you want to flatten:
tronbox flatten contracts/Box.sol
In this case, the result will contain the source code of Box.sol and all its transitive dependencies (the files that it imports, and the files that those files import, and so on).
You can also use multiple files:
tronbox flatten contracts/Box.sol contracts/Foo.sol
However, if Foo.sol is a dependency of Box.sol, then the result will be the same as in the previous example.
As mentioned in the previous section, you can redirect the output to some file:
tronbox flatten contracts/Box.sol > Flattened.sol