diff --git a/hoobuddy.cabal b/hoobuddy.cabal
--- a/hoobuddy.cabal
+++ b/hoobuddy.cabal
@@ -1,5 +1,5 @@
 name:                hoobuddy
-version:             0.1.0.0
+version:             0.1.0.1
 synopsis:            Simple tool for fetching and merging hoogle data
 description:
  Hoobuddy parses the specified cabal project file and invokes hoogle to fetch databases for
@@ -20,6 +20,7 @@
 executable hoobuddy
   hs-source-dirs:      src
   main-is:             Main.hs
+  other-modules:       Hoobuddy
   ghc-options:         -fwarn-incomplete-patterns
   build-depends:       base >=4.7 && <4.8
                      , Cabal
@@ -31,6 +32,7 @@
                      , hoogle >= 4.2.34
                      , process
                      , bytestring
+                     , mtl
 
 
   default-language:    Haskell2010
diff --git a/src/Hoobuddy.hs b/src/Hoobuddy.hs
new file mode 100644
--- /dev/null
+++ b/src/Hoobuddy.hs
@@ -0,0 +1,68 @@
+module Hoobuddy where
+
+import Distribution.Package
+import Distribution.PackageDescription
+import Distribution.PackageDescription.Parse
+import System.Exit
+import System.Directory
+import Data.List (isSuffixOf)
+import System.Process
+import System.IO (hGetContents)
+import System.FilePath.Posix (dropExtension)
+import Data.Functor ((<$>))
+
+
+data Hoobuddy = Hoobuddy {
+                           databases :: String
+                         , useBase   :: Bool
+                         , custom    :: [String]
+                         } deriving (Show)
+
+type StdOut = String
+type StdErr = String
+
+-- | Prints dependencies from cabal file
+deps :: FilePath -> IO ()
+deps  path = do
+        pkgs <- getDeps path
+        putStrLn $ unlines pkgs
+
+-- | Returns list of dependencies from cabal file
+getDeps :: FilePath -> IO [String]
+getDeps cabal = do
+        contents <- readFile cabal
+        let depInfo = parsePackageDescription contents
+        case depInfo of
+            ParseFailed _ -> exitWith (ExitFailure 1)
+            ParseOk _ d     -> return (packageNames $ extractDeps d)
+        where
+            packageNames :: [Dependency] -> [String]
+            packageNames  = map (init . tail . head . tail . words . show . pkg)
+            pkg :: Dependency -> PackageName
+            pkg (Dependency x _) = x
+
+extractDeps :: GenericPackageDescription -> [Dependency]
+extractDeps d = ldeps ++ edeps
+  where ldeps = case condLibrary d of
+                Nothing -> []
+                Just c -> condTreeConstraints c
+        edeps = concatMap (condTreeConstraints . snd) $ condExecutables d
+
+-- | Returns a list of available ".hoo" files
+getHooDatabases :: FilePath -> IO [String]
+getHooDatabases p = do
+    files <- getDirectoryContents p
+    return $ filter (\x -> ".hoo" `isSuffixOf`  x) files
+
+-- | Calls hoogle to fetch all packages specified
+hoogleFetch :: [String] -> IO (Either (ExitCode, StdErr) StdOut)
+hoogleFetch [] = return (Right "No data to fetch")
+hoogleFetch pkgs =  do
+    (_, Just hOut, Just hErr, pHandle) <- createProcess (proc "hoogle" ("data":pkgNames)) {std_out = CreatePipe, std_err = CreatePipe}
+    exitCode <- waitForProcess pHandle
+    stdOut <- hGetContents hOut
+    stdErr <- hGetContents hErr
+    return (if exitCode == ExitSuccess then Right stdOut else Left (exitCode, stdErr))
+        where
+            pkgNames = dropExtension <$> pkgs
+
diff --git a/src/Main.hs b/src/Main.hs
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -4,7 +4,6 @@
 
 import GHC.Generics
 import System.Environment (getArgs)
-import System.Exit
 import Data.Aeson hiding (encode)
 import Data.Yaml
 import Data.List
@@ -12,7 +11,7 @@
 import System.FilePath.Posix
 import Hoogle (defaultDatabaseLocation, mergeDatabase)
 import Control.Applicative
-import Control.Monad (filterM, liftM, unless)
+import Control.Monad.Error
 import Data.Maybe (isJust)
 
 import Hoobuddy
@@ -37,36 +36,37 @@
 
 help :: IO ()
 help = putStrLn $
-    unlines [ "Usage : hoobuddy [deps|build] <cabal-file>"
+    unlines [ "Usage : hoobuddy [deps|fetch] <cabal-file>"
             , "                 [--help]"
             , "                 [--default]"
             , ""
             , "deps         list configured dependencies"
-            , "build        do stuff yet to be defined"
+            , "fetch        fetch and merge documentation databases"
             , ""
             , "--default    prints the default configuration"
             , "--help       prints this help"
             ]
 
+type HoobuddyAction = ErrorT String IO
+
 main :: IO ()
 main = do
-    exitIfHoogleMissing
     conf <- loadConfig
     args <- getArgs
-    run conf args where
-        run _ ["deps", file]          = deps file
-        run conf  ["build", file]     = build file conf
-        run _ ["--help"]              = help
-        run _ ["--default"]           = defaultConfig >>= \x -> putStrLn $ unpack $ encode x
-        run _ _ = do
-            help
-            exitWith (ExitFailure 1)
+    ret <- runErrorT $ runHoobuddy conf args
+    either putStrLn (\_ -> putStrLn "") ret
 
--- | Exits with error code if hoogle isn't installed
-exitIfHoogleMissing :: IO ()
-exitIfHoogleMissing = do
-    hoogleInstalled <- liftM isJust (findExecutable "hoogle")
-    unless hoogleInstalled (putStrLn hoogleMissingError >> exitWith (ExitFailure 1))
+runHoobuddy :: Hoobuddy -> [String] -> HoobuddyAction ()
+runHoobuddy cfg args = do
+    hoogleInstalled <- liftM isJust (liftIO $ findExecutable "hoogle")
+    unless hoogleInstalled (throwError hoogleMissingError)
+    run cfg args
+        where
+            run _     ["deps", file]      = liftIO $ deps file
+            run conf  ["fetch", file]     = build file conf
+            run _     ["--help"]          = liftIO help
+            run _     ["--default"]       = liftIO $ defaultConfig >>= \x -> putStrLn $ unpack $ encode x
+            run _ _                       = liftIO help
 
 
 -- | Loads configuration from file or uses defaults
@@ -89,28 +89,29 @@
     return $ either (const Nothing) Just parseResult
 
 
-build :: FilePath -> Hoobuddy -> IO ()
+build :: FilePath -> Hoobuddy -> HoobuddyAction ()
 build cabalFile conf = do
-    pkgs <- map (++ ".hoo") <$> getDeps cabalFile
-    dbs <- getHooDatabases (databases conf)
+    pkgs <- map (++ ".hoo") <$> liftIO (getDeps cabalFile)
+    dbs <- liftIO $ getHooDatabases (databases conf)
 
     let allPkgs = (++) pkgs (if useBase conf then defaultPkgs else custom conf)
     let available = allPkgs `intersect` dbs
     let missing = filter (`notElem` available) allPkgs
 
-    printInfo "Fetching databases for: " missing
-    hoogleFetch missing >>= \x -> case x of
-        Right _             -> return ()
-        Left (code, stderr) -> putStrLn ("hoogle exited with error:\n" ++ stderr) >> exitWith code
+    liftIO $ if null missing
+     then putStrLn "No data needs to be fetched"
+     else printInfo "Fetching databases for: " missing
+    fetchOp <- liftIO $ hoogleFetch missing
+    either (\_ -> throwError "Error executing hoogle") (\_ -> return ()) fetchOp
 
-    putStrLn "Merging databases ..."
-    currDir <- getCurrentDirectory
-    existingDbs <- filterM doesFileExist (fmap (databases conf </>) allPkgs)
-    mergeDatabase  existingDbs (currDir </> "default.hoo")
+    liftIO $ putStrLn "Merging databases ..."
+    currDir <- liftIO getCurrentDirectory
+    existingDbs <- liftIO $ filterM doesFileExist (fmap (databases conf </>) allPkgs)
+    liftIO $ mergeDatabase existingDbs (currDir </> "default.hoo")
+    liftIO $ putStrLn "Success: default.hoo"
 
 -- | Pretty printer for info output
 printInfo :: String -> [String] -> IO ()
-printInfo _ [] = return ()
 printInfo str xs = putStrLn $ str ++ "[" ++ intercalate "," xs ++ "]"