XMonad.Util.Loggers

A collection of simple logger functions and formatting utilities which can be used in the ppExtras field of a pretty-printing status logger format. See XMonad.Hooks.DynamicLog for more information.

Usage

Use this module by importing it into your ~/.xmonad/xmonad.hs:

import XMonad.Util.Loggers

Then, add one or more loggers to the ppExtras field of your PP, possibly with extra formatting . For example:

  -- display load averages and a pithy quote along with xmonad status.
  , logHook = dynamicLogWithPP $ def {
                 ppExtras = [ padL loadAvg, logCmd "fortune -n 40 -s" ]
               }
  -- gives something like " 3.27 3.52 3.26 Drive defensively.  Buy a tank."

See the formatting section below for another example using a where block to define some formatted loggers for a top-level myLogHook.

Loggers are named either for their function, as in battery, aumixVolume, and maildirNew, or are prefixed with "log" when making use of other functions or by analogy with the pp* functions. For example, the logger version of ppTitle is logTitle, and logFileCount loggerizes the result of file counting code.

Formatting utility names are generally as short as possible and carry the suffix "L". For example, the logger version of shorten is shortenL.

Of course, there is nothing really special about these so-called "loggers": they are just X (Maybe String) actions. So you can use them anywhere you would use an X (Maybe String), not just with DynamicLog.

Additional loggers welcome!

type Logger = X (Maybe String)

Logger is just a convenient synonym for X (Maybe String).

System Loggers

aumixVolume :: Logger

Get the current volume with aumix. http://jpj.net/~trevor/aumix.html

battery :: Logger

Get the battery status (percent charge and charging/discharging status). This is an ugly hack and may not work for some people. At some point it would be nice to make this more general/have fewer dependencies (assumes /usr/bin/acpi and sed are installed.)

date :: String -> Logger

Get the current date and time, and format them via the given format string. The format used is the same as that used by the C library function strftime; for example, date "%a %b %d" might display something like Tue Feb 19. For more information see something like http://www.cplusplus.com/reference/clibrary/ctime/strftime.html.

loadAvg :: Logger

Get the load average. This assumes that you have a utility called /usr/bin/uptime and that you have sed installed; these are fairly common on GNU/Linux systems but it would be nice to make this more general.

maildirNew :: FilePath -> Logger

Get a count of new mails in a maildir.

maildirUnread :: FilePath -> Logger

Get a count of unread mails in a maildir. For maildir format details, to write loggers for other classes of mail, see http://cr.yp.to/proto/maildir.html and logFileCount.

logCmd :: String -> Logger

Create a Logger from an arbitrary shell command.

logFileCount

Arguments

:: FilePath

directory in which to count files

-> (String -> Bool)

predicate to match if file should be counted

-> Logger

Get a count of filtered files in a directory. See maildirUnread and maildirNew source for usage examples.

XMonad Loggers

A very small sample of what you can log since you have access to X. For example you can loggerize the number of windows on each workspace, or titles on other workspaces, or the id of the previously focused workspace....

logCurrent :: Logger

Get the name of the current workspace.

logLayout :: Logger

Get the name of the current layout.

logTitle :: Logger

Get the title (name) of the focused window.

Formatting Utilities

Combine logger formatting functions to make your ppExtras more colorful and readable. (For convenience this module exports <$> to use instead of '.' or '$' in hard to read formatting lines. For example:

myLogHook = dynamicLogWithPP def {
    -- skipped
    , ppExtras = [lLoad, lTitle, logSp 3, wrapL "[" "]" $ date "%a %d %b"]
    , ppOrder = \(ws,l,_,xs) -> [l,ws] ++ xs
    }
  where
    -- lTitle = fixedWidthL AlignCenter "." 99 . dzenColorL "cornsilk3" "" . padL . shortenL 80 $ logTitle
    -- or something like:
    lTitle = fixedWidthL AlignCenter "." 99 <$> dzenColorL "cornsilk3" "" <$> padL . shortenL 80 $ logTitle

    lLoad = dzenColorL "#6A5ACD" "" . wrapL loadIcon "   " . padL $ loadAvg
    loadIcon = " ^i(/home/me/.dzen/icons/load.xbm)"

Note: When applying shortenL or fixedWidthL to logger strings containing colors or other formatting commands, apply the formatting after the length adjustment, or include "invisible" characters in the length specification, e.g. in the above '^fg(cornsilk3)' and '^fg()' yields 19 invisible and 80 visible characters.

onLogger :: (String -> String) -> Logger -> Logger

Use a string formatting function to edit a Logger string. For example, to create a tag function to prefix or label loggers, as in 'tag: output', use:

tagL l = onLogger $ wrap (l ++ ": ") ""

   tagL "bat" battery
   tagL "load" loadAvg

If you already have a (String -> String) function you want to apply to a logger:

revL = onLogger trim

See formatting utility source code for more onLogger usage examples.

wrapL :: String -> String -> Logger -> Logger

Wrap a logger's output in delimiters, unless it is X (Nothing) or X (Just ""). Some examples:

   wrapL " | " " | " (date "%a %d %b") -- ' | Tue 19 Feb | '

   wrapL "bat: " "" battery            -- ' bat: battery_logger_output'

fixedWidthL

Arguments

:: Align

AlignCenter, AlignRight, or AlignLeft

-> String

String to cycle to pad missing logger output

-> Int

Fixed length to output (including invisible formatting characters)

-> Logger

-> Logger

Make a logger's output constant width by padding with the given string, even if the logger is X (Nothing) or X (Just ""). Useful to reduce visual noise as a title logger shrinks and grows, to use a fixed width for a logger that sometimes becomes Nothing, or even to create fancy spacers or character based art effects.

It fills missing logger output with a repeated character like ".", ":" or pattern, like " -.-". The cycling padding string is reversed on the left of the logger output. This is mainly useful with AlignCenter.

logSp :: Int -> Logger

Create a "spacer" logger, e.g. logSp 3 -- loggerizes ' '. For more complex "spacers", use fixedWidthL with return Nothing.

padL :: Logger -> Logger

Pad a logger's output with a leading and trailing space, unless it is X (Nothing) or X (Just "").

shortenL :: Int -> Logger -> Logger

Limit a logger's length, adding "..." if truncated.

dzenColorL :: String -> String -> Logger -> Logger

Color a logger's output with dzen foreground and background colors.

 dzenColorL "green" "#2A4C3F" battery

xmobarColorL :: String -> String -> Logger -> Logger

Color a logger's output with xmobar foreground and background colors.

 xmobarColorL "#6A5ACD" "gray6" loadAverage

(<$>) :: Functor f => (a -> b) -> f a -> f b infixl 4

An infix synonym for fmap.

The name of this operator is an allusion to $. Note the similarities between their types:

 ($)  ::              (a -> b) ->   a ->   b
(<$>) :: Functor f => (a -> b) -> f a -> f b

Whereas $ is function application, <$> is function application lifted over a Functor.

Examples

Convert from a Maybe Int to a Maybe String using show:

>>> show <$> Nothing
Nothing
>>> show <$> Just 3
Just "3"

Convert from an Either Int Int to an Either Int String using show:

>>> show <$> Left 17
Left 17
>>> show <$> Right 17
Right "17"

Double each element of a list:

>>> (*2) <$> [1,2,3]
[2,4,6]

Apply even to the second element of a pair:

>>> even <$> (2,2)
(2,True)