From: Steven Barth <steven@midlink.org>
Date: Tue, 17 Feb 2015 13:41:04 +0000 (+0100)
Subject: example: prevent script from running in parallel to avoid races
X-Git-Tag: debian/1.1+git20160131-1~33
X-Git-Url: https://git.decadent.org.uk/gitweb/?p=odhcp6c.git;a=commitdiff_plain;h=29b9032cbef27bc60a20c955d607537fedd554af

example: prevent script from running in parallel to avoid races
---

diff --git a/odhcp6c-example-script.sh b/odhcp6c-example-script.sh
index 6215257..a1fb0fc 100755
--- a/odhcp6c-example-script.sh
+++ b/odhcp6c-example-script.sh
@@ -6,7 +6,7 @@ update_resolv() {
 	local dns="$2"
 	
 	(
-		flock -n 9
+		flock 9
 		grep -v "#odhcp6c:$device:" /etc/resolv.conf > /tmp/resolv.conf.tmp
 		for c in $dns; do
 			echo "nameserver $c #odhcp6c:$device:" >> /tmp/resolv.conf.tmp
@@ -131,23 +131,25 @@ teardown_interface() {
 	update_resolv "$device" ""
 }
 
-case "$2" in
-	bound)
-		teardown_interface "$1"
-		setup_interface "$1"
-	;;
-	informed|updated|rebound|ra-updated)
-		setup_interface "$1"
-	;;
-	stopped|unbound)
-		teardown_interface "$1"
-	;;
-	started)
-		teardown_interface "$1"
-	;;
-esac
-
-# user rules
-[ -f /etc/odhcp6c.user ] && . /etc/odhcp6c.user
-
-exit 0
+(
+	flock 9
+	case "$2" in
+		bound)
+			teardown_interface "$1"
+			setup_interface "$1"
+		;;
+		informed|updated|rebound|ra-updated)
+			setup_interface "$1"
+		;;
+		stopped|unbound)
+			teardown_interface "$1"
+		;;
+		started)
+			teardown_interface "$1"
+		;;
+	esac
+
+	# user rules
+	[ -f /etc/odhcp6c.user ] && . /etc/odhcp6c.user
+) 9>/tmp/odhcp6c.lock.$1
+rm -f /tmp/odhcp6c.lock.$1