main :: IO ()
main = do
    opts <- getOpts
    if null (inputs opts)
        then showUsage
        else runMain (run opts)
main :: IO ()
main = do
    opts <- getOpts
    if null (inputs opts)
        then showUsage
        else runMain (run opts)
main = do
    opts <- getOpts
    if null (inputs opts)
        then showUsage
        else runMain (run opts)