Added function into a files not in zshrc

.local/bin/cidr2mask

@@ -0,0 +1,21 @@
+#!/bin/bash
+cidr2mask() {
+    local i mask=""
+    local full_octets=$(($1 / 8))
+    local partial_octet=$(($1 % 8))
+
+    for ((i = 0; i < 4; i += 1)); do
+        if [ $i -lt $full_octets ]; then
+            mask+=255
+        elif [ $i -eq $full_octets ]; then
+            mask+=$((256 - 2 ** (8 - partial_octet)))
+        else
+            mask+=0
+        fi
+        test $i -lt 3 && mask+=.
+    done
+
+    echo $mask
+}
+
+cidr2mask "$@"