From dc81200eeacfc0e3bbf5a893640a64d1504d9932 Mon Sep 17 00:00:00 2001
From: Alexey Samoshkin <al.samoshkin@gmail.com>
Date: Tue, 21 Nov 2017 16:00:49 +0200
Subject: [PATCH 1/2] Implement memory calculation for Linux systems

---
 scripts/helpers.sh |  5 +++++
 scripts/mem.sh     | 38 +++++++++++++++++++++++++++++++++-----
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/scripts/helpers.sh b/scripts/helpers.sh
index 75429ab..b9ff115 100755
--- a/scripts/helpers.sh
+++ b/scripts/helpers.sh
@@ -20,6 +20,11 @@ is_osx() {
   [ $(uname) == "Darwin" ]
 }
 
+is_linux(){
+  [ $(uname -s) == "Linux" ]
+}
+
+
 command_exists() {
   local command="$1"
   type "$command" >/dev/null 2>&1
diff --git a/scripts/mem.sh b/scripts/mem.sh
index 899d91b..6951f6d 100755
--- a/scripts/mem.sh
+++ b/scripts/mem.sh
@@ -44,10 +44,9 @@ print_mem() {
   local size_format
   
   if is_osx; then
+    mem_usage=$(get_mem_usage_linux)
+  elif is_linux; then 
     mem_usage=$(get_mem_usage_osx)
-  else 
-    #  TODO: implement memory calculation for linux
-    mem_usage="TODO"
   fi
 
   # get_mem_usage* function returns values in KiB
@@ -87,8 +86,6 @@ print_mem() {
   # Calculate colors for mem and swap
   local mem_color=$(get_mem_color "$mem_pused")
   local swap_color=$(get_swap_color "$swap_pused")
-
-  echo $mem_view_tmpl;
   
   local mem_view="$mem_view_tmpl"
   mem_view="${mem_view//'#{mem.used}'/$(printf "$size_format" "$mem_used" "$size_unit")}"
@@ -144,6 +141,37 @@ get_mem_usage_osx(){
   printf "%s %s %s" "$free_used" "$swap_free" "$swap_used"
 }
 
+
+# Method #1. Sum up free+buffers+cached, treat it as "available" memory, assuming buff+cache can be reclaimed. Note, that this assumption is not 100% correct, buff+cache most likely cannot be 100% reclaimed, but this is how memory calculation is used to be done on Linux
+
+# Method #2. If "MemAvailable" is provided by system, use it. This is more correct method, because we're not relying on fragile "free+buffer+cache" equation. 
+
+# See: Interpreting /proc/meminfo and free output for Red Hat Enterprise Linux 5, 6 and 7 - Red Hat Customer Portal - https://access.redhat.com/solutions/406773
+
+# See: kernel/git/torvalds/linux.git - /proc/meminfo: provide estimated available memory - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773
+get_mem_usage_linux(){
+  local mem_free_used=$( </proc/meminfo awk '
+    BEGIN { total=0; free=0; }
+      /MemTotal:/ { total=$2; }
+      
+      /MemFree:/ { free+=$2; }
+      /Buffers:/ { free+=$2; }
+      /Cached:/ { free+=$2; }
+
+      /MemAvailable:/ { free=$2; exit;}
+    END { print free, total-free }
+  ')
+
+  local swap_free_used=$( </proc/meminfo awk '
+    BEGIN { total=0; free=0; }
+      /SwapTotal:/ { total=$2; }
+      /SwapFree:/ { free=$2; }
+    END { print free, total-free }
+  ')
+
+  printf "%s %s" "$mem_free_used" "$swap_free_used"
+}
+
 main() {
   print_mem
 }

From 335997c678d5dd0871e6980a29e805315bdb6f27 Mon Sep 17 00:00:00 2001
From: Alexey Samoshkin <al.samoshkin@gmail.com>
Date: Tue, 21 Nov 2017 18:04:02 +0200
Subject: [PATCH 2/2] Fix wrong OSX/Linux condition for memory calculation

---
 scripts/mem.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/mem.sh b/scripts/mem.sh
index 6951f6d..354d284 100755
--- a/scripts/mem.sh
+++ b/scripts/mem.sh
@@ -44,9 +44,9 @@ print_mem() {
   local size_format
   
   if is_osx; then
-    mem_usage=$(get_mem_usage_linux)
-  elif is_linux; then 
     mem_usage=$(get_mem_usage_osx)
+  elif is_linux; then 
+    mem_usage=$(get_mem_usage_linux)
   fi
 
   # get_mem_usage* function returns values in KiB