ovs-docker: Use a different mechanism to check for commands.

Currently, the script uses '--version' option from different commands
to check for their availability. uuidgen on Centos6 has been reported
not to have the '--version' option causing failure in script invocation.

This commit looks for the utilities in $PATH instead. The code is
copied from build-aux/dist-docs.

Reported-by: Michael J. Smalley <[email protected]>
Suggested-by: Ben Pfaff <[email protected]>
Signed-off-by: Gurucharan Shetty <[email protected]>
Acked-by: Ben Pfaff <[email protected]>

AUTHORS

@@ -286,6 +286,7 @@ Maxime Brun             [email protected]
 Madhu Venugopal         [email protected]
 Michael A. Collins      [email protected]
 Michael Hu              [email protected]
+Michael J. Smalley      [email protected]
 Michael Mao             [email protected]
 Michael Shigorin        [email protected]
 Mihir Gangar            [email protected]

utilities/ovs-docker

@@ -13,14 +13,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-check_command_avail () {
-    while [ $# -ne 0 ]; do
-        if ("$1" --version) > /dev/null 2>&1; then :; else
-            echo >&2 "$UTIL: missing $1, cannot proceed"
-            exit 1
+# Check for programs we'll need.
+search_path () {
+    save_IFS=$IFS
+    IFS=:
+    for dir in $PATH; do
+        IFS=$save_IFS
+        if test -x "$dir/$1"; then
+            return 0
         fi
-        shift
     done
+    IFS=$save_IFS
+    echo >&2 "$0: $1 not found in \$PATH, please install and try again"
+    exit 1
 }
 
 ovs_vsctl () {
@@ -201,7 +206,9 @@ EOF
 }
 
 UTIL=$(basename $0)
-check_command_avail ovs-vsctl docker uuidgen
+search_path ovs-vsctl
+search_path docker
+search_path uuidgen
 
 if (ip netns) > /dev/null 2>&1; then :; else
     echo >&2 "$UTIL: ip utility not found (or it does not support netns),"\