1 files changed, 12 insertions, 0 deletions
diff --git a/bin/netmask-to-prefix b/bin/netmask-to-prefix
new file mode 100755
index 000000000..1c4dbeb28
--- /dev/null
+++ b/bin/netmask-to-prefix
@@ -0,0 +1,12 @@
+#! /bin/sh
+set -euf
+
+netmask=$1
+
+binaryNetmask=$(echo $1 | sed 's/^/obase=2;/;s/\./;/g' | bc | tr -d \\n)
+binaryPrefix=$(echo $binaryNetmask | sed -n 's/^\(1*\)0*$/\1/p')
+if ! echo $binaryPrefix | grep -q .; then
+  echo $0: bad netmask: $netmask >&2
+  exit 4
+fi
+printf %s $binaryPrefix | tr -d 0 | wc -c