Added function into a files not in zshrc

.local/bin/mask2cidr

@@ -0,0 +1,20 @@
+#!/bin/bash
+mask2cidr() {
+    local mask=$1
+
+    # In RFC 4632 netmasks there's no "255." after a non-255 byte in the mask
+    local left_stripped_mask=${mask##*255.}
+    local len_mask=${#mask}
+    local len_left_stripped_mask=${#left_stripped_mask}
+
+    local conversion_table=0^^^128^192^224^240^248^252^254^
+    local number_of_bits_stripped=$(((len_mask - len_left_stripped_mask) * 2))
+    local signifacant_octet=${left_stripped_mask%%.*}
+
+    local right_stripped_conversion_table=${conversion_table%%$signifacant_octet*}
+    local len_right_stripped_conversion_table=${#right_stripped_conversion_table}
+    local number_of_bits_from_conversion_table=$((len_right_stripped_conversion_table / 4))
+    echo $((number_of_bits_stripped + number_of_bits_from_conversion_table))
+}
+
+mask2cidr "$@"