diff --git a/lib/utils.zsh b/lib/utils.zsh
index 6ff7b0f..c625010 100644
--- a/lib/utils.zsh
+++ b/lib/utils.zsh
@@ -6,3 +6,7 @@ pid_for() {
     echo $(lsof -n -i ":$1" | grep LISTEN)
 
 }
+
+intersect_files() {
+    comm -23 <(cat $1) <(cat $2)
+}