produce decoded transaction in stderr

to avoid interfering with possible scripting

README.md

@@ -2,6 +2,6 @@
 
 The aim is to create a trustworthy Stellar transaction signer (and, by necessity, a pretty printer) using only Glasgow Haskell compiler code and Haskell Core libraries, reducing the possible supply chain attack surface.
 
-To build and run it, install `cabal-install` and use `cabal run`.
+To build and run it, install `cabal-install` and use `cabal run`. The program expects your transaction coming from the standard input, and your private (S...) key residing in `$HOME/~/.stellar-veritas-key`. It will produce the decoded transaction description afterwards, with simple descriptions of the most popular operations. When it is ran from an interactive terminal, it will ask for a confirmation before signing the transaction.
 
 The project contains the code of trimmed-down non-core dependencies, mainly cryptographic libraries. To avoid using bundled libraries (to build against the current Hackage), do the same in the `src` directory. To further reduce the amount of code under audit, weeder can be used, although the utility is dubious.

src/Main.hs

@@ -31,7 +31,7 @@ main = do
   let parsedTransaction = case xdrDeserialize transaction :: Either String TransactionEnvelope of
         Left err -> error err
         Right x -> x
-  T.putStrLn $ pretty parsedTransaction
+  T.hPutStrLn stderr $ pretty parsedTransaction
   proceed <- confirm
   when proceed $ do
     key <- getPrivateKey