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+% A Tool to Manage a Set of YAML Objects Representing Account Information — pwutil
+
+A long time ago I wrote a bunch of scripts (first in bash, then zsh, and later perl) to manage a, sometimes encrypted, file containing account information I get asked to create and remember on a daily basis—accounts for shopping websites spring to mind.
+
+[pwutil](git://git.yggdrasil.li/pwutil) is the newest iteration in this line of bunches of scripts.
+
+## Features
+
+  * Support for embedding common operation in any kind of record keeping
+
+    Thus support for almost any encryption known to man (with absolutely no online security), version control, and synchronisation
+  * [Human readable](https://en.wikipedia.org/wiki/YAML) backstore
+  * [Command Line Interface](https://en.wikipedia.org/wiki/Command-line_interface)-only
+  * New accounts can be partially generated by user defined functions with out of the box support for [pwgen](http://sourceforge.net/projects/pwgen/) and SSH
+
+## Documentation
+
+I shall document the project in a partial and file-wise fashion—amendments available on request.
+
+### Structure
+
+~~~ {#DirTree}
+pwutil
+├── default.nix
+├── PWAdd.hs
+├── PWGet.hs
+├── PWUtil
+│   ├── Encfs.hs
+│   ├── Extra
+│   │   ├── PWGen.hs
+│   │   └── SSHCmd.hs
+│   ├── Types.hs
+│   └── Util.hs
+├── pwutil.hs
+├── PWUtil.hs
+└── pwutil.nix
+~~~
+
+### `pwutil.nix`
+is a [nix](https://nixos.org/nix) expression allowing easy installation using the nix package manager.
+A `~/.nixpkgs/config.nix` allowing one to do so might look thus:
+~~~ {.numberLines}
+{
+  packageOverrides = pkgs: {
+    pwutil = pkgs.callPackage /path/to/pwutil.nix {};
+  };
+}
+~~~
+
+### `Types.hs`
+
+`PWLocation` describes the location of a file containing a YAML object mapping human readable identifiers to account information.
+`encryption`, which has essentially the same signature as [`withFile`](http://hackage.haskell.org/package/base-4.8.0.0/docs/System-IO.html#v:withFile) wraps all access to the file.
+This in an extremely powerful way to deal with any kind of encryption desired (currently I implemented automatic mounting of an [EncFs](http://en.wikipedia.org/wiki/EncFS) container and `plain`, which does nothing.
+`create` is used to try and create the location once should access fail due to a file [not existing](http://hackage.haskell.org/package/base-4.8.0.0/docs/System-IO-Error.html#v:doesNotExistErrorType).
+
+~~~ {#Types.hs .haskell .numberLines}
+module PWUtil.Types (
+  PWLocation(..),
+  Encryption(..),
+  PW(..),
+  PWConfig(..),
+  Generator(..)
+  ) where
+
+import System.IO (Handle(..), IOMode(..))
+import Control.Monad.State
+import qualified Data.Map as M
+import Data.Yaml
+
+data PWLocation = PWLocation
+                  { path :: FilePath
+                  , encryption :: Encryption
+                  , create :: IO ()
+                  }
+
+instance Show PWLocation where
+  show loc = show $ path loc
+
+type Encryption = FilePath -> IOMode -> (Handle -> IO ()) -> IO ()
+
+type PW = StateT PWConfig IO
+
+data PWConfig = PWConfig
+               { location :: PWLocation
+               , generators :: M.Map String Generator
+               }
+
+type Generator = [String] -> IO Value
+~~~
+
+
+### `pwutil.hs`
+
+is, in a [xmonad](http://xmonad.org) kind of way, the configuration file.
+
+~~~ {#pwutil.hs .haskell .numberLines}
+import PWUtil
+
+import System.FilePath ((</>))
+import qualified Data.Map as M
+import System.Directory (getHomeDirectory)
+
+pWLocation :: IO PWLocation
+pWLocation = do
+  h <- getHomeDirectory
+  return PWLocation { path = h </> "accounts.yaml"
+                    , encryption = plain
+                    , create = createFile $ h </> "accounts.yaml"
+                    }
+
+myGenerators :: M.Map String Generator
+myGenerators = M.empty
+
+main :: IO ()
+main = do
+  myLocation <- pWLocation
+  runPW (PWConfig { location = myLocation, generators = myGenerators }) pwutil
+~~~
+
+### `Encfs.hs`
+
+shall serve as an example for a module providing an encryption wrapper.
+It exports
+
+~~~{.haskell}
+encfs :: Encfs -> Encryption
+encfs (Encfs backStore mountpoint) = …
+~~~
+
+Upon execution it checks whether `mountpoint` is already mounted.
+If not it executes `encfs backStore mountpoint` interactively and calls `fusermount -u` after completion.