1 files changed, 6 insertions, 2 deletions
diff --git a/swift-storage.configure b/swift-storage.configure
index f410bea6..078a8390 100644
--- a/swift-storage.configure
+++ b/swift-storage.configure
@@ -20,9 +20,13 @@ set -e
 export ROOT="$1"
 
 validate_number() {
-    if ! echo -n "$2" | grep -xq '[0-9]\+'
+    local name="$1"
+    local value="$2"
+
+    local pattern='[0-9]+'
+    if ! [[ "$value" =~ $pattern ]]
     then
-        echo "'$1' must be a number" >&2
+        echo "'$name' must be a number" >&2
         exit 1
     fi
 }