From 2d8a89d6be28c995478794531748e4c7b0a3b9d4 Mon Sep 17 00:00:00 2001
From: Samuel Fadel <samuel@nihil.ws>
Date: Tue, 20 Jun 2023 14:18:54 +0200
Subject: Added naive wrapper to run scripts as singletons.

* bin/singleton: Added.
---
 bin/singleton | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100755 bin/singleton

diff --git a/bin/singleton b/bin/singleton
new file mode 100755
index 0000000..e11ed71
--- /dev/null
+++ b/bin/singleton
@@ -0,0 +1,17 @@
+#!/bin/sh
+#
+# Simple script wrapper to force another script to run as a singleton:
+# prevents multiple instances of it (the same command name; naive)
+# from running.
+
+LOCKFILE="/tmp/singleton-$1"
+LOCKFD=9
+
+lock()      { flock -$1 $LOCKFD; }
+stop_lock() { lock u; lock xn && rm -f $LOCKFILE; }
+prep_lock() { eval "exec $LOCKFD>\"$LOCKFILE\""; trap stop_lock EXIT; }
+
+prep_lock
+lock xn || exit 1
+
+exec $@
-- 
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