Replace poor man's synchronization primitive (i.e. sleep) with a wait

until construct in the hopes of making these tests less flaky.

regress/usr.bin/tail/follow-overwrite-data.sh

@@ -1,9 +1,11 @@
 #!/bin/sh
 #
-# $OpenBSD: follow-overwrite-data.sh,v 1.2 2012/11/03 08:41:25 ajacoutot Exp $
+# $OpenBSD: follow-overwrite-data.sh,v 1.3 2024/12/21 07:49:03 anton Exp $
 
 # test if tail follows a file overwritten by data
 
+. "$(dirname "${0}")/util.sh"
+
 #set TMPDIR to a nfs-based dir for nfs testing
 DIR=$(mktemp -d)
 echo DIR=${DIR}
@@ -30,8 +32,7 @@ echo 'baar' > ${DIR}/bar
 # smaller data without delay
 echo 'bar' > ${DIR}/bar
 
-# hey nfs !
-sleep 5
+wait_until "[ `grep -c bar ${OUT}` = 2 ]"
 kill ${PID}
 diff -u ${OUT} ${0%%.sh}.out || exit 1
 [ $(grep -c "tail: ${DIR}/bar has been truncated, resetting." ${ERR}) -eq 3 ] || exit 2

regress/usr.bin/tail/util.sh

@@ -0,0 +1,13 @@
+# $OpenBSD: util.sh,v 1.1 2024/12/21 07:49:03 anton Exp $
+
+wait_until() {
+	local _i=0
+
+	while [ "$_i" -lt 8 ]; do
+		sh -x -c "$*" && return 0
+		sleep 0.5
+		_i="$((_i + 1))"
+	done
+	echo timeout
+	return 1
+}