From 60668406425eeb14bcec9f68cf592cad449a7061 Mon Sep 17 00:00:00 2001
From: Daniel Porter <dporter@nyx.com>
Date: Mon, 28 Apr 2014 19:26:59 +0100
Subject: [PATCH] Better logic to determine required Docker version

This commit adds support for both a minimum Docker version, and the
version currently recommended by Docker development team. If the user is
not running the minimum version, the script will not continue. User is
warned if they have any version prior to the currently recommended
version.
---
 launcher | 39 +++++++++++++++++++++++++++++++++++----
 1 file changed, 35 insertions(+), 4 deletions(-)

diff --git a/launcher b/launcher
index ca777c1..ba26532 100755
--- a/launcher
+++ b/launcher
@@ -6,6 +6,9 @@ opt=$3
 
 cd "$(dirname "$0")"
 
+docker_min_version='0.9.1'
+docker_rec_version='0.10.0'
+
 config_file=containers/"$config".yml
 cidfile=cids/"$config".cid
 cidbootstrap=cids/"$config"_boostrap.cid
@@ -38,6 +41,27 @@ usage () {
   exit 1
 }
 
+compare_version() {
+    declare -a ver_a
+    declare -a ver_b
+    IFS=. read -a ver_a <<< "$1"
+    IFS=. read -a ver_b <<< "$2"
+
+    while [[ -n $ver_a ]]; do
+        if (( ver_a > ver_b )); then
+            return 0
+        elif (( ver_b > ver_a )); then
+            return 1
+        else
+            unset ver_a[0]
+            ver_a=("${ver_a[@]}")
+            unset ver_b[0]
+            ver_b=("${ver_b[@]}")
+        fi
+    done
+    return 1  # They are equal
+}
+
 prereqs() {
 
   # 1. docker daemon running?
@@ -59,14 +83,21 @@ prereqs() {
     exit 1
   fi
 
-  # 3. running docker 0.10+
-  test=`$docker_path --version | grep 0.10`
+  # 3. running recommended docker version
+  test=($($docker_path --version))  # Get docker version string
+  test=${test[2]//,/}  # Get version alone and strip comma if exists
 
-  if [[ "$test" =~ "0.10" ]] ; then : ; else
-    echo "Your Docker installation is old, please upgrade to 0.10.0 or up"
+  # At least minimum version
+  if compare_version "${socker_min_version}" "${test}"; then
+    echo "ERROR: Docker version ${test} not supported, please upgrade to at least ${docker_min_version}, or recommended ${docker_rec_version}"
     exit 1
   fi
 
+  # Recommend best version
+  if compare_version "${docker_rec_version}" "${test}"; then
+    echo "WARNING: Docker version ${test} deprecated, recommend upgrade to ${docker_rec_version} or newer."
+  fi
+
   # 4. able to attach stderr / out / tty
   test=`$docker_path run -i --rm -a stdout -a stderr $image echo working`
   if [[ "$test" =~ "working" ]] ; then : ; else
-- 
2.25.1