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.

diff --git a/launcher b/launcher
index ca777c12290ee416839217c5de1ca2380f722569..ba2653223e8e2582632d3b3efa5651de3d236f51 100755 (executable)
--- 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