dbueno:
> Hi all,
>
> In a command-line app of mine I want to have a --version flag, like
> many GNU apps do to report their version. The only way I know to
> provide the version number is to hardcode it in the source code
> somewhere. That means I have the version number in two places: the
> .cabal file and the source code. I just know that one day they'll get
> unsynchronised, and --version will be wrong.
>
> Is there any way to put the version number in _one_ place, and have
> both the .cabal and source refer to it? Or even any easier way to
> synchronise both version numbers?
Yes, cabal provides support for this. Here's how we do that in xmonad.
In your program, import the magic module Paths_$progname:
import Paths_xmonad (version)
["--version"] -> putStrLn ("xmonad " ++ showVersion version)
which provides many fields from the .cabal file used to compile the
program.
In your .cabal file , have something like:
name: xmonad
version: 0.8.1
Problem solved :)
Look in
$ vim dist/build/autogen/Paths_xmonad.hs
to see what you get to play with:
module Paths_xmonad (
version,
getBinDir, getLibDir, getDataDir, getLibexecDir,
getDataFileName
) where
import Data.Version (Version(..))
import System.Environment (getEnv)
version :: Version
version = Version {versionBranch = [0,8,1], versionTags = []}
bindir, libdir, datadir, libexecdir :: FilePath
bindir = "/home/dons/.cabal/bin"
libdir = "/home/dons/.cabal/lib/xmonad-0.8.1/ghc-6.10.1"
datadir = "/home/dons/.cabal/share/xmonad-0.8.1"
libexecdir = "/home/dons/.cabal/libexec"
getBinDir, getLibDir, getDataDir, getLibexecDir :: IO FilePath
getBinDir = catch (getEnv "xmonad_bindir") (\_ -> return bindir)
getLibDir = catch (getEnv "xmonad_libdir") (\_ -> return libdir)
getDataDir = catch (getEnv "xmonad_datadir") (\_ -> return datadir)
getLibexecDir = catch (getEnv "xmonad_libexecdir") (\_ -> return libexecdir)
getDataFileName :: FilePath -> IO FilePath
getDataFileName name = do
dir <- getDataDir
return (dir ++ "/" ++ name)
-- Don
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