From 77a603a904087dd9fd3350da029f279f076e4f4b Mon Sep 17 00:00:00 2001
From: Hiltjo Posthuma <hiltjo@codemadness.org>
Date: Sun, 31 Jan 2016 15:31:17 +0100
Subject: sfeed_update: fix issue with merging failed feeds

When fetching a feed failed and its temporary file was stored (filesize=0)
it would still be merged with the (possible) old file. This updated the
modification time which would be used in the next poll (If-Modified-Since).

The solution is to check if the file is non-empty and only then merge, this
is still not 100% fool-proof, but much better.
---
 sfeed_update | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/sfeed_update b/sfeed_update
index eafbcfe..8185345 100755
--- a/sfeed_update
+++ b/sfeed_update
@@ -78,14 +78,17 @@ feed() {
 
 	# get new data and merge with old.
 	sfeedfilenew="${sfeedpath}/${name}.new"
-	# if file exists, merge
-	if [ -e "${sfeedfile}" ]; then
-		merge "${sfeedfile}" "${tmpfeedfile}" > "${sfeedfilenew}"
-		# overwrite old file with updated file
-		mv "${sfeedfilenew}" "${sfeedfile}"
-	else
-		# else just copy
-		mv "${tmpfeedfile}" "${sfeedfile}"
+	# new feed data is non-empty.
+	if [ -s "${tmpfeedfile}" ]; then
+		# if file exists, merge
+		if [ -e "${sfeedfile}" ]; then
+			merge "${sfeedfile}" "${tmpfeedfile}" > "${sfeedfilenew}"
+			# overwrite old file with updated file
+			mv "${sfeedfilenew}" "${sfeedfile}"
+		else
+			# else just copy
+			mv "${tmpfeedfile}" "${sfeedfile}"
+		fi
 	fi) &
 }
 
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