added kill_prev snippet

Author: saminjay

snippets/bash/system/kill-prev-session.md

@@ -0,0 +1,20 @@
+---
+title: Kill Previous Instance
+description: Kill all previous instances of a script
+author: saminjay
+tags: kill,process,background
+---
+
+```bash
+function kill_prev() {
+    # $$ contains current pid (grep ignore so it doesn't suicide)
+    local processes
+    readarray -t processes < <(pgrep -f "$0" | grep -v "$$")
+    kill "${processes[@]}" >/dev/null 2>&1
+}
+
+# Usage:
+# Add this function to your background running script
+# It will make sure that only one instance of your script is running at a time
+kill_prev
+```