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+---
+title: A Tool to Manage a Set of YAML Objects Representing Account Information — pwutil
+published: 2015-04-07
+---
+
+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 read- and writeable](https://en.wikipedia.org/wiki/YAML) backstore
+  * Machine parseable output
+  * [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
+
+## Usage
+
+~~~
+pwget [<searchTerm> …]
+Looks up and returns all accounts which contain any <searchTerm> anywhere in their representation — case insensitive.
+
+pwadd [[--gen-<generator> [<generatorArgument> …] …] --] <identifier> [<attributeKey> <attributeValue> …]
+Adds an account to the store — does not overwrite.
+~~~
+
+## 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
+│   ├── 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 {};
+  };
+}
+~~~
+
+The derivation takes some arguments (write those in `{}` above):
+
+`main ? null`
+  ~ Overwrite `pwutil.hs` with a file path
+
+`with<Package> ? false`
+  ~ `<Package>` is one of Pwgen, or Ssh a the current time.
+    If `true` wraps executables to have `$PATH` include `<Package>`.
+
+### `Types.hs`
+
+Introducing `PW` (much as [xmonad](https://xmonad.org) did with `X`) is an easy way to keep track of the `PWConfig` without resorting to function arguments.
+`BackStore` is our (new and improved) way of encapsulating store access in a totally customisable way—`plain`, which is essential `readFile` and `writeFile` as provided by `ByteString`, is provided for convenience in `Util.hs`.
+`PWConfig` most importantly contains a definition of generators (called by passing `--gen-…` to `pwadd`).
+
+~~~ {#Types.hs .haskell .numberLines}
+module PWUtil.Types (
+  PW(..),
+  BackStore(..),
+  PWConfig(..),
+  Generator(..)
+  ) where
+
+import Control.Monad.State
+import qualified Data.Map as M
+import Data.Yaml
+import Data.ByteString
+
+type PW = StateT PWConfig IO
+
+data BackStore = BackStore
+                 { readContents :: PW ByteString
+                 , writeContents :: ByteString -> PW ()
+                 }
+
+data PWConfig = PWConfig
+                { generators :: M.Map String Generator
+                , backstore :: BackStore
+                }
+                      
+type Generator = [String] -> PW Value
+~~~
+
+
+### `pwutil.hs`
+
+is, in a [xmonad](http://xmonad.org) kind of way, the configuration file—the shipped default is reproduced below as a template for custom configs.
+
+~~~ {#pwutil.hs .haskell .numberLines}
+import PWUtil
+
+import System.FilePath ((</>))
+import System.Directory (getHomeDirectory)
+
+main :: IO ()
+main = do
+  h <- getHomeDirectory
+  runPW (emptyConfig { backstore = plain (h </> "accounts.yaml") }) pwutil
+~~~