Load: new load average monitor

Closes #208

5 files changed, 73 insertions, 2 deletions

diff --git a/changelog.md b/changelog.md
index daaf121..d5d00d7 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,10 @@
+## Version 0.43 (unreleased)
+
+_New features_
+
+  - New monitor `Load` providing load averages (stolen from Finn
+    Lawler).
+
 ## Version 0.42 (March, 2022)
 
 _New features_
diff --git a/doc/plugins.org b/doc/plugins.org
index 462256f..81f50f9 100644
--- a/doc/plugins.org
+++ b/doc/plugins.org
@@ -662,7 +662,21 @@
           Run Locks
         #+end_src
 
-*** Process Monitors
+*** Load and Process Monitors
+***** =Load Args RefreshRate=
+
+      - Aliases to =load=
+
+      - Args: default monitor arguments. The low and high thresholds
+        (=-L= and =-H=) refer to load average values.
+
+      - Variables that can be used with the =-t/--template= argument:
+        =load1=, =load5=, =load15=.
+
+      - Default template: =Load: <load1>=.
+
+      - Displays load averages for the last 1, 5 or 15 hours.
+
 ***** =TopProc Args RefreshRate=
 
       - Aliases to =top=
diff --git a/src/Xmobar/Plugins/Monitors.hs b/src/Xmobar/Plugins/Monitors.hs
index 8fd31b7..9a3e3de 100644
--- a/src/Xmobar/Plugins/Monitors.hs
+++ b/src/Xmobar/Plugins/Monitors.hs
@@ -3,7 +3,7 @@
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Xmobar.Plugins.Monitors
--- Copyright   :  (c) 2010, 2011, 2012, 2013, 2017, 2018, 2019, 2020 Jose Antonio Ortega Ruiz
+-- Copyright   :  (c) 2010-2013, 2017-2020, 2022 Jose Antonio Ortega Ruiz
 --                (c) 2007-10 Andrea Rossato
 -- License     :  BSD-style (see LICENSE)
 --
@@ -30,6 +30,7 @@ import Xmobar.Plugins.Monitors.Cpu
 import Xmobar.Plugins.Monitors.MultiCpu
 import Xmobar.Plugins.Monitors.Batt
 import Xmobar.Plugins.Monitors.Bright
+import Xmobar.Plugins.Monitors.Load
 import Xmobar.Plugins.Monitors.Thermal
 import Xmobar.Plugins.Monitors.ThermalZone
 import Xmobar.Plugins.Monitors.CpuFreq
@@ -65,6 +66,7 @@ data Monitors = Network      Interface   Args Rate
               | Battery      Args        Rate
               | DiskU        DiskSpec    Args Rate
               | DiskIO       DiskSpec    Args Rate
+              | Load         Args        Rate
               | Thermal      Zone        Args Rate
               | ThermalZone  ZoneNo      Args Rate
               | Memory       Args        Rate
@@ -124,6 +126,7 @@ instance Exec Monitors where
 #endif
     alias (Network i _ _) = i
     alias (DynNetwork _ _) = "dynnetwork"
+    alias (Load _ _) = "load"
     alias (Thermal z _ _) = z
     alias (ThermalZone z _ _) = "thermal" ++ show z
     alias (Memory _ _) = "memory"
@@ -176,6 +179,7 @@ instance Exec Monitors where
     start (Thermal z a r) = runM (a ++ [z]) thermalConfig runThermal r
     start (ThermalZone z a r) =
       runM (a ++ [show z]) thermalZoneConfig runThermalZone r
+    start (Load a r) = runM a loadConfig runLoad r
     start (Memory a r) = runM a memConfig runMem r
     start (Swap a r) = runM a swapConfig runSwap r
     start (Battery a r) = runM a battConfig runBatt r
diff --git a/src/Xmobar/Plugins/Monitors/Load.hs b/src/Xmobar/Plugins/Monitors/Load.hs
new file mode 100644
index 0000000..238d374
--- /dev/null
+++ b/src/Xmobar/Plugins/Monitors/Load.hs
@@ -0,0 +1,45 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Plugins.Monitors.Load
+-- Copyright   :  Finn Lawler
+-- License     :  BSD-style (see LICENSE)
+--
+-- Author      :  Finn Lawler <flawler@cs.tcd.ie>
+-- Maintainer  :  jao <mail@jao.io>
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- A load average monitor for Xmobar.  Adapted from
+-- Xmobar.Plugins.Monitors.Thermal by Juraj Hercek.
+--
+-----------------------------------------------------------------------------
+
+module Xmobar.Plugins.Monitors.Load (loadConfig, runLoad) where
+
+import Xmobar.Plugins.Monitors.Common
+import qualified Data.ByteString.Lazy.Char8 as B
+import System.Posix.Files (fileExist)
+
+-- | Default configuration.
+loadConfig :: IO MConfig
+loadConfig = mkMConfig
+       "Load: <load1>" -- template
+       ["load1", "load5", "load15"]       -- available replacements
+
+-- | Parses the contents of a loadavg proc file, returning
+-- the list of load averages
+parseLoadAvgs :: B.ByteString -> [Float]
+parseLoadAvgs =
+  map ((read :: String -> Float) . B.unpack) . take 3 . B.words . head . B.lines
+
+-- | Retrieves load information.  Returns the monitor string parsed
+-- according to template (either default or user specified).
+runLoad :: [String] -> Monitor String
+runLoad _ = do
+  let file = "/proc/loadavg"
+  exists <- io $ fileExist file
+  if exists then
+      (do l <- io $ B.readFile file >>= return . parseLoadAvgs
+          parseTemplate =<< mapM (showWithColors $ showDigits 2) l)
+    else
+      return "Load: N/A"
diff --git a/xmobar.cabal b/xmobar.cabal
index 8126f53..51cbd14 100644
--- a/xmobar.cabal
+++ b/xmobar.cabal
@@ -167,6 +167,7 @@ library
                    Xmobar.Plugins.Monitors.CpuFreq,
                    Xmobar.Plugins.Monitors.Disk,
                    Xmobar.Plugins.Monitors.Disk.Common,
+                   Xmobar.Plugins.Monitors.Load,
                    Xmobar.Plugins.Monitors.Mem,
                    Xmobar.Plugins.Monitors.MultiCoreTemp,
                    Xmobar.Plugins.Monitors.MultiCpu,