[ovs-dev] [PATCH] utilities/ovs-docker: Fix broken check_command_avail function

[Michael Smalley]

Reported-by: Michael J. Smalley <michaeljsmalley at gmail.com>
Tested-by: Michael J. Smalley <michaeljsmalley at gmail.com>
Signed-off-by: Michael J. Smalley <michaeljsmalley at gmail.com>

This logic was breaking on a CentOS 6.6 box with all dependencies (ovs-vsctl,
docker, and uuidgen) installed and working. The check_command_avail function
checks to see if the commands exist by running "$command --version". This is
flawed logic because it assumes "--version" will work with all of the commands
that are listed in the function call. It's much more common (and future proof)
to simply check to see that the required binaries are available by running the
"which" command. Also, I added a ! to make the control structure a little more
terse.

Evidence of the problem with checking --version:
[root at docker ~]# uuidgen --version
uuidgen: invalid option -- '-'
Usage: uuidgen [-r] [-t]
[root at docker ~]# echo $?
1

---
 utilities/ovs-docker | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/utilities/ovs-docker b/utilities/ovs-docker
index 48908b1..d0b5f81 100755
--- a/utilities/ovs-docker
+++ b/utilities/ovs-docker
@@ -15,10 +15,7 @@

 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
-        fi
+        if ! $(which "$1" > /dev/null); then echo >&2 "$UTIL: missing
$1, cannot proceed"; exit 1; fi
         shift
     done
 }
--
1.9.3 (Apple Git-50)